G7 Python II

Python ll

Computer Science

Binary Language

Introduction to Python

Variables

Comments

Assignment Operator

Data Types

Mathematical Tools in Python

Arithmetic Operators

Strings

Strings Concatenation and Repetition Input and

String

Introduction to Programming

Computers are incredible and powerful machines. Today, they are everywhere, be it in a shop, a bank, a school, government offices, or malls. But they don’t do anything without our instructions. They are helpful, but deep down, they are not smart. The instructions we give to a computer are sets of commands to perform a task, which is nothing but programs.

We need a language to instruct computers to carry out a task, just as we use English to communicate with one another. Since computers are machines, they can only understand machine language. As machines are electrically powered devices, they listen to two signals: on and off, which are represented by 0s and 1s, respectively.

Binary Language

The language that is formed with 0s and 1s is called binary language, as it builds up on two digits. Binary language is also known as low level language.

Programming Language

A programming language is a language which has its own vocabulary and syntax just like we have in English, Hindi and other languages.

Programming is the process of creating a set of instructions that tells a computer how to perform a task. A task is a piece of work to be done. In a program, it may represent a section of the program.

Programming Languages are classified into two categories:

● Low-level languages

● High-level languages

Low-Level Language

Machine-friendly language is called low-level language (LLL). Low-level languages include machine and assembly languages. They communicate with the computer directly. As a result, no language translation is required.

High-Level language

A high-level language (HLL) is a human-friendly programming language like Java, Python, C, etc. It is intended to make computer programming simpler for programmers, as it is not feasible for programmers to remember the 0 and 1 codes for everything. Later, these high-level language (HLL) programs are translated into low-level language (LLL) programs to allow computers to understand them.

The high level language we are going to learn now is Python.

Introduction to Python

Guido van Rossum developed Python at the National Research Institute for Mathematics and Computer Science in the Netherlands in the 1990s.

Python is a high-level, interpreted, interactive, object-oriented programming language. It is the easiest of the existing programming languages and super reliable.

Python is not named after a real Python, but rather after Guido’s favourite comedy show, Monty Python’s Flying Circus.

Features of Python

1. Easy to Read: Python code is easy to read, just like English.

2. Quick to Learn: Python has few keywords, a simple structure, and a clearly defined syntax. This makes learning Python easy and quick.

3. Easy to Maintain: Python’s source code is fairly easy to maintain.

4. Interactive Execution Mode: Python offers script and interactive modes for running programmes. The code can be interactively tested and debugged in the interactive mode.

A three-step loop process defines how Python is run in the interactive window:

● The Python interpreter first reads the code entered at the prompt.

● Then it evaluates the code.

● Finally, it prints the outcome and awaits new input. The acronym REPL stands for read-evaluate-print loop.

5. Dynamic Typing: Python defines data type dynamically for the objects according to the value assigned. Also, it supports dynamic data type checking.

6. Portable: Python is a portable language because it can be used on a variety of hardware platforms.

7. Rich Standard Library: Python has a rich, portable and cross-platform standard library.

8. Large Database Support: Python provides interfaces to all major commercial databases.

9. GUI Application Creation: Python also supports the creation of GUI applications.

10. Scalable: Python provides better structure and support for larger programs than shell scripting. This makes it scalable.

Execution of a Python Code

The Python interpreter runs the code line by line and displays the results until an error occurs. It changes the HLL-written source code into bytecode, an intermediate language, which is then converted back into machine language and executed.

Syntax

Every language has its own set of rules for writing. All programming languages also have rules for writing programs in them. These rules are called syntaxes.

Python also has some rules that we need to follow while writing a program.

One of Python’s rules is that it is a case-sensitive language, which means that num, Num, and nUm all refer to different things.

Syntax Error

Syntax errors are mistakes in following the rules to write the code, such as wrong function name, missing quotes, brackets, etc.

Below are two examples of common syntax errors:

1. Missed double quotes

2. Missed symbols, such as a colon, comma, or brackets CODE

print(Learn Python SyntaxError: invalid syntax

The print() Statement

The print() statement displays a value or information in the output.

Syntax: print("value") CODE

print("Hello kitty!")Hello kitty!

CODEOUTPUT print(25)25

We can also print multiple elements in a single print statement by separating them with a comma. While printing them, each element in the output is separated by white spaces.

Syntax: print("box1","box2")

print("Hello","everyone!") Hello everyone!

print("You","are","welcome!") You are welcome!

The sep And end Parameter

The sep and end are optional parameters in the print function in Python. By default, the print function has whitespace as a separator between words and ends with a newline.

With sep parameter you can replace whitespace with your choice of separator to separate words and with end parameter you can add a symbol or value at the end of the statement.

Syntax: print("box1", "box2", sep= "symbol")

CODE

print("I am fine","well","alright","tired", sep = "/") print("What are you reading", end="?")

Solved Example

Write a program to print the following:

180-455-2020

1*2*3*4*5*6*7 =7! 10*20*30=6000

Answer: CODE

1. print('180','455','2020',sep='-')

2. print(1,2,3,4,5,6,7,sep='*',end='=7!')

3. print(10,20,30,sep='*',end=' = ') print(10*20*30)

Variables

OUTPUT

I am fine/well/alright/ tired

What are you reading?

A variable is a memory location on a computer which can hold any value and can also change over time as needed.

To understand it in an easy way, think of it like a box in which you can store a number and later you can replace that number with another number.

In simple words, variables are names given to the memory location where your value is stored.

The figure below illustrates three variables with their respective values. The three variables used in the figure are “name”, “winner” and “score”. The variable “name” holds the value “Bob”, the variable “winner” holds the value “True”, and the variable “score” holds the value “35”.

Therefore, whenever the variable “name” is used in the program, it refers directly to its value, “Bob”.

Creating a Variable

In Python, variable declaration and initialisation happens with a single step of assigning a value to a variable.

Syntax: variable_name = value

We can also initialise multiple variables in one line.

Syntax: var1, var2 = value1, value2

1. word, number = "hi", 5

2. print(word,number) hi 5

NOTE: If we change the value of a variable and use it again, the old value is replaced with the new value.

Rules of Naming a Variable

There are certain rules we need to follow while naming a variable. Some rules are:

1. The name of a variable should be meaningful.

2. Only the underscore ( _ ) symbol can be used while naming variables.

3. A variable name must start with a letter or the underscore character.

1. greeting_message = "Good Evening!"

2. _number_ = 205

3. print(greeting_message)

1. greeting%message = "Good day!"

2. print(greeting%message)

Good Evening! 205

SyntaxError: cannot assign to operator

4. As Python is a case-sensitive language, variable names are also casesensitive.

Example: old, Old and OLD are three different variables.

CODEOUTPUT

1. num = 25

2. Num = 30

3. NUM = 45

4. print(num)

5. print(Num)

25 30 45 8 Python II

5. A variable name can have numbers within but cannot begin with a number.

Case Styles in Python

As we have case styles for words in English, we have some case styles for naming variables. Below are the case styles you can follow to name variables in Python:

1. Camel Case

A variable name can be written in camel case if it contains two or more distinct words. In camel case, we write the name of the variable as the first word in lowercase and all subsequent words with the first letter capitalised without a space in between.

Example: “Name of the company” can be written as “nameOfTheCompany”.

As this represents the camel’s hump we call it Camel-Case.

First word lowercase Capitalise All Following Words

1. camelCaseExample = "Hello Camel" 2. print(camelCaseExample) Hello Camel

2. Snake Case

Snake-case is the practice of writing in which each space is replaced by an underscore ( _ ) character and the first letter of each word written in lowercase.

Example: “Name of the company” in snake-case is written as “name_of_ the_company”.

Comments

It is always a good practice to document your work. In programming, we also document our projects to keep them organised and easily understandable by other programmers.

We use comments to add documentation to a Python program. Python ignores these lines of comments in the program during execution as they are not part of the code.

Benefits of Using Comments

Comments help:

● Structure the code and make it easier for humans to read.

● Explain the thought processes and intentions behind the code.

● Find errors and debug the code.

● Reuse the code in other applications as well.

After all, there is a popular saying, “Anyone can write code that a computer can understand. Good programmers write code that humans can understand.”

1. snake_case_example = "Hello Python"

2. print(snake_case_example) Hello Python

In Python, we have two types of comments:

1. Single-line Comment

2. Multi-line Comment

Single-Line Comment

A single-line comment starts with a hash character ( # ) and is followed by related information.

1. #using the print command

2. print("Learn Programming")

3.

4. greeting = "Learn" #defining the greeting

5. name = "Python" #defining the name

6. print(greeting, name)

Multi-Line Comment

Learn Programming Learn Python

A multi-line comment begins and ends with three single or double-quote characters (‘ ‘ ‘ or “ “ ‘) with related information enclosed.

1. '''

2. This is an example of

3. Multiline comments

4. '''

5. """

6. Printing hello world with sep command

7. Printing hello world with end command

8. """

9. print("learn", "coding", sep = "#")

Solved Examples

Example 2.1

learn#coding

11 Chapter 1 • Introduction to Programming

Answer:

side = 80 areaOfSquare=side*side print("The area is: ", areaOfSquare)

Example 2.2

The area is: 6400

Below are the average temperatures of different places and store them in different variables. The temperature has increased by 0.5 in the afternoon and displays the updated temperature of all the places in the same format shown below.

OUTPUT

Place Temperature Zo Hills 20

Met Town 25 Bay Area 26

Answer: CODE

Zo_Hills=20 Met_Town=25 Bay_Area=26

print("Place","Temperature") print("Zo Hills", Zo_Hills+1) print("Met_Town",Met_Town+1) print("Bay_Area",Bay_Area+1)

Assignment Operator

The ‘=’ operator is known as assignment operator, also read as ‘is set to’. It assigns the value on the right-hand side of the “=” symbol to the variable on the left-hand side.

“=” in Math vs “=” in Python

There is a difference between the “=” we use in Maths and the one we use in Python.

In mathematics, = means to equate the left-hand side with the right-hand side. It is the sign of equality.

In python, = symbol is used to set the value of the left-hand side variable to the right-hand side variable.

Syntax: variable = value

# the value is stored in the variable variable = variable + value

# value is added to existing variable value and stored in the variable

Assignment Statement

A line of the program that tells Python to assign a value to a variable is called an assignment statement. The variable on the left of “=” holds/stores the value on the right.

Syntax: variable_name=value

1. name="Rashi"

2. roll_no=28

3. print(name)

Rashi 28

Solved Examples

Example 3.1

Classify the following into either Animal or Tree, and then print all the Animal variables in the first line and Plant variables in the second line.

“Cat, Banyan, Monkey, Lion, Teak, Neem”

OUTPUT

Animals - Cat, Monkey, Lion

Trees - Banyan, Teak, Neem

Answer: CODE

animal_1,animal_2,animal_3 = "Cat","Monkey","Lion" tree_1,tree_2,tree_3="Banyan","Teak","Neem" print("Animals -", animal_1,animal_2,animal_3) print("Trees -", tree_1,tree_2,tree_3)

Example 3.2

A fruit shop sells 32 apples, 33 bananas, 20 strawberries, and 15 oranges. Print the percentage of fruit sold that were apples or oranges.

OUTPUT

Total Fruit sold =100 47% of fruit sold were apples or oranges.

Hint: Store the number of fruit sold in variables. Print the total number of fruit sold.

Find the percentage using the formula (apples+oranges)/total*100.

Answer: CODE

apple=32

banana=33

strawberry=20

orange=15

total_sold=apple+banana+strawberry+orange percent_apple_orange_sold=apple+orange/total_sold*100 print('Total Fruit sold =',total_sold)

Data Types

Data types define what type of data a variable, a named memory location, can hold.

The default data types in Python are as follows:

Data Type Description Example

Integer (int) Stores non-decimal numbers in a variable. 5, -8, 43, 54685, -5612965

Float (float) Stores decimal point numbers in a variable. 6.8, -3.2

String (str) Stores words and characters in a variable. “Hello”, ”World”

Boolean (bool) Stores two values: True and False in a variable True and False

The type() Function

The type() function returns the data type of the value held by the variable.

Syntax: type(variable_name)

CODE

number_ = 5

word_ = "Hi"

print(type(number_))

print(type(word_))

Type casting

OUTPUT

<class 'int'>

<class 'str'>

Type casting refers to converting data type of a variable into another.

Type Casting to Integer

The int() function is used to typecast the value of a variable into integer. It converts the following data type into integer:

1. Float by removing the decimal point and everything after it.

2. String only if string represents a number.

3. Boolean by converting True to 1 and False to 0.

Syntax: int(variable_name)

1. str_to_int = int("8")

2. bool_to_int = int(True)

3. print(str_to_int, type(str_to_int))

4. print(bool_to_int, type(bool_to_int))

8 <class 'int'>

1 <class 'int'>

1. number=int("Python")ValueError: invalid literal for int() with base 10: 'Python'

Type Casting to Float

The float() function is used to typecast the value of a variable into float. It converts the following data type into float:

1. Integer by adding a decimal followed by a zero.

2. String only if the string represents a float or an integer.

Syntax: float(variable_name)

1. num=float(65)

2. flat_no=float("101")

3. print(num)

4. print(flat_no)

1. str=float("Learn")

2. print(str)

Type Casting to String

ValueError: could not convert string to float: 'Learn'

The str() function is used to typecast the value of a variable into a string. It converts all the data types including float, integer, boolean into a string.

Syntax: str(variable_name) CODE

1. num1 = str(25)

2. num2 = str(17.2)

3. print(num1 , type(num1))

4. print(num2, type(num2))

Type Casting to Boolean

25 <class 'str'>

17.2 <class 'str'>

The bool() function is used to typecast the value of a variable into boolean. It converts the following data type into boolean:

1. Integer and prints False if the value of the variable is 0, otherwise prints True.

2. String and prints False if the string is empty, otherwise prints True.

Syntax: bool(variable_name) CODE

1. a=bool(0)

2. b=bool(1)

3. c=bool("")

4. d=bool("Programming")

False True False True

Difference between String and Boolean

Strings are written by enclosing a set of characters within a pair of single or double quotes.

Strings are a series of characters that form words and sentences.

Solved Examples

Example 4.1

A boolean variable can take only one of the two boolean values represented by the words True or False without quotes.

Booleans are either 0 or 1. They are used to categorise something in either True or False, which also implies a Yes or a No.

Make 2 variables, one to store the city name and the other for the pincode. Change the pincode to string to print the city name and pin code in the format given below.

OUTPUT

City Name Pincode

Roseville 6584796

Answer: CODE

name="Roseville"

pin=65847961

print('City Name','Pincode')

print(name , str(pin))

Mathematical Tools in Python

Maths Library

The Python Math Library provides common maths functions that can be used for complex mathematical computations. Math library contains functions such as ceil, floor, factorial, etc.

We need to import the math library into our program before we can use the functions.

Here is how we import the library.

Syntax: import math

Here are a few useful mathematical functions used in daily computations.

The ceil() function

The ceil comes from the word ceiling. As the name suggests ceil() function rounds UP the number to the nearest integer (i.e., the smallest integer greater than or equal to that number) and returns the value.

Syntax: ceil(value)

The floor() function

As the name suggests, the floor() function rounds a number DOWN to the nearest integer (i.e., the largest integer not greater than the number) and returns the value.

Syntax: floor(value)

1. import math

2. number = 1.666666666666667

3. ceil_ = math.ceil(number)

4. floor_ = math.floor(number)

5. print("Number rounded UP to ceil is:",ceil_)

6. print("Number rounded DOWN to floor is:",floor_)

The round() function

Number rounded UP to ceil is: 2

Number rounded DOWN to floor is: 1

The round() function returns a float value by rounding off the number to the decimal place that we give as input. The function takes in two values, the number we want to round off and the decimal places we want to round to (i.e., the number of digits after the decimal point).

The default number of decimals is 0, i.e. the function will return the nearest integer.

Syntax: round(float_value,digits_after_decimalpoint)

The Random Module

Python’s Random module is an in-built module of Python which is used to generate random numbers. The random module contains functions like random(), randint() etc.

The Random() Function

The random() function generates random floating numbers between 0 and 1.

Syntax: random.random()

The Randint() Function

The randint() function returns an integer number within the specified range. The specified range from which we want the integer is given as input in the function.

Syntax: random.randint(start,end)

1. import random 2. print(random.randint(3,50))

Solved Examples

Example 5.1

Prepare your report card:

Store your name and marks in 5 subjects in different variables, and calculate your percentage of marks.

Now, display the following data as well.

1. Percentage of marks scored in 5 subjects.

2. Round-up the percentage using ceil function.

3. Round-down the percentage using the floor function.

4. Round the percentage to 3 decimal places.

OUTPUT

Name of the student: John

Percentage of the student: 79.4%

Percentage after using ceil(): 80%

Percentage after using floor(): 79%

Percentage after using round(): 79.4%

Answer:

1. import math

2. name="John" #you can write any name

3. marks1=94

4. marks2=84

5. marks3=92

6. marks4=58

7. marks5=69

8.

9. percentage=(marks1+marks2+marks3+marks4+marks5)*100/500

10.

11. print("Name of the student:", name)

12. print("Percentage of the student:",percentage,"%")

13. print("Percentage after using ceil():",math.ceil(percentage),"%")

14. print("Percentage after using floor():",math. floor(percentage),"%")

15. print("Percentage after using round():",round(percentage,3),"%")

Arithmetic Operators

Arithmetic operators in Python are used along with the integer or float values to perform mathematical operations on them.

There are 7 arithmetic operators in Python:

BEMDAS Rule

Whenever there is a mathematical expression in Python, it solves it in the following sequence:

1. Brackets (B)

2. Exponents (E)

3. Multiplication (M)

4. Division (D)

5. Addition (A)

6. Subtraction (S)

Python solves the mathematical expression in the order above from left to right of their occurrence.

But, whenever multiple exponent operators are used in an expression, Python solves the exponent part from right to left

Example:

9 + 7 * (8 - 4) / 2 - 3**2

= 9 + 7 * 4 / 2 - 3**2

(First, the brackets are solved.)

= 9 + 7 * 4 / 2 - 9

= 9 + 28 / 2 - 9

= 9 + 14 - 9

= 23 - 9

(Then, Exponent is solved.)

(Then, multiplication is solved.)

(Then, division is solved.)

(Then, addition is solved.)

= 14 (Finally, subtraction is solved.)

Solved Examples

Example 6.1

As a programmer, write a program to help Dave with the right answers to the questions given below using operators in Python.

a = 23 b = 13

a) Addition of a and b.

b) Multiplication of a and b.

c) Division of a and b.

d) Base a to the power b.

e) Modulus of a/b

OUTPUT

Addition of a and b is: 36

Multiplication of a and b is: 299

a divided by b is: 1.7692307692307692

Base a to the power b is: 504036361936467383

Remainder, when a is divided by b, is: 10

Answer: CODE

1. a,b=23,13

2. print("Addition of a and b is:",a+b)

3. print("Multiplication of a and b is:",a*b)

4. print("a divided by b is:",a/b)

5. print("Base a to the power b is:",a**b)

6. print("Remainder, when a is divided by b, is:",a%b)

Strings

A string is a data type that represents a sequence of characters. In Python, strings are put inside double quotes (“ ”) or single quotes (‘ ’). These values can be words, symbols, characters, numbers, or a combination of all these.

A string can be categorised into two as follows:

● A single-line string

● A multi-line string

Single-Line String

A single-line string can be enclosed in either single quotes or double quotes.

CODE OUTPUT

1. name1="Mohit"

2. name2='Mohit'

3. print(name1)

4. print(name2)

Multi-Line String

Mohit Mohit

A multi-line string can be enclosed in either three single quotes (‘) or three double-quotes (“).

CODE OUTPUT

1. proverb_1= '''Don't judge

2. a book

3. by its cover. '''

4.

5. proverb_2= """

6. Beauty is

7. in the eye of

8. the beholder.

9. """

10. print(proverb_1)

11. print(proverb_2)

Escaping (\)

Don't judge a book by its cover.

Beauty is in the eye of the beholder.

When we have multiple apostrophes in a sentence, python throws an error as it is illegal.

We can avoid this with the help of an escape character. An escape character is a backslash ( \ ) followed by the character that is to be inserted.

An example of an illegal character is a double quote inside a string that is surrounded by double quotes:

print("Let us learn "Python".")SyntaxError: invalid syntax

Thus if there are multiple apostrophes and we want them to be part of the same string we use backslashes before them so that the character is included in the string.

print("Let us learn \"Python\".") Let us learn "Python".

Newline(\n)

In some cases we might need to break the string into multiple lines.

In order to add a new line, we put \n before the character where we want the string to break, the characters after the \n are printed on the next line onwards. CODE

print("Creative\nMinds") Creative Minds

Solved Examples

Example 1.1

Teacher has asked you to write two thoughts for the day. Write a program to print the two sentences given below using ONLY ONE print.

OUTPUT

One kind word can change someone's day. No one is perfect. That's why pencils have erasers.

Answer: CODE print("One kind word can change someone\'s day.\nNo one is perfect. That\'s why pencils have erasers.")

Strings Concatenation and Repetition

Concatenation

Concatenation is the technique of combining two or more strings together. There are different ways to concatenate strings.

Using + Operator

The addition operator (+) has a different meaning in the case of strings. The + operator is used to join two or more strings into one single string.

CODE OUTPUT

a= "Think"

b = "Different"

c = a + b

print(c)

The join() Function

ThinkDifferent

The join() string function returns a string by joining all the elements of a string.

Syntax: str.join([var1, var2])

var1 = "Hello"

var2 = "World" print("".join([var1, var2]))

String Repetition

The (*) operator duplicates the string and combines them.

If * is used with an integer, it performs multiplication, but if it is used with strings, it performs repetition.

Syntax: repeated_string = string1*no_of_times

Multiplying a string with an integer, repeats the string that many times.

str = "Challenge" print(str*3)

ChallengeChallengeChallenge

Multiplying a string with a float gives an error. We can only repeat strings with integers.

CODE

str = "Coding" print(str*3.5)

Solved Examples

Example 2.1

TypeError: can't multiply sequence by non-int of type 'float'

In a game app the name of a player is stored as FirstName and LastName. Now do the following tasks.

1. Create the player by concatenating the FirstName and LastName.

2. Create a temporary password by repeating the username twice.

3. Print a welcome message “Greetings, BayMax” using the join() method.

Username is: BayMax

Temporary password is: BayMaxBayMaxBayMax

Greetings, BayMax

Answer:

first_name = "Bay"

last_name = "Max"

CODE

username = first_name+last_name print("Username is:",username)

temp_password = username*3 print("Temporary password is:",temp_password)

welcome_message = "".join(["Greetings, ",username]) print(welcome_message)

Input and Formatting

The input() Function

The input() function in Python is used to take and store input from the user.

We can take any kind of information from the users as input. Whatever is entered as input, the input() function converts it to a string.

Syntax: input("message to be shown in input prompt")

CODE

x = input("Enter your name: ") print("Hello, " + x+"!")

The islower() Function

OUTPUT

Enter your name: Saansh Hello, Saansh!

The islower() function returns True if all the characters in a string are in lower case, otherwise it returns False.

Syntax: string.islower()

greetings_1 = "welcome to our world!"

check_1 = greetings_1.islower()

print(check_1)

greetings_2 = "Welcome to our world!"

check_2 = greetings_2.islower()

print(check_2)

If a string contains symbols and numbers only, the function returns False.

If symbols and numbers are present along with lowercase characters, it returns True

(i.e., Symbols and numbers are ignored by the function)

sentence_1 = "#%@&^"

check_1 = sentence_1.islower()

print(check_1)

sentence_2 = "user@uolo.in"

check_2 = sentence_2.islower()

print(check_2)

The isupper() Function

The isupper() function returns True if all the characters are in upper case, otherwise it returns False.

Symbols and numbers are ignored by this function as well.

Syntax: string.isupper()

proverb_1 = "NOTHING IS IMPOSSIBLE"

check_1 = proverb_1.isupper()

print(check_1)

proverb_2 = "NOTHING is IMPOSSIBLE"

check_2 = proverb_2.isupper()

print(check_2)

The lower() Function

The lower() function is used to convert all the characters of a string to lowercase.

Syntax: string.lower()

statement = "Listen, THINK and LEARN"

x = statement.lower() print(x)

The upper() Function

listen, think and learn

The upper() function is used to convert all the characters of a string to uppercase.

Syntax: string.upper()

sentence = "Do this right!"

x = sentence.upper() print(x)

Solved Examples

Example 3.1

DO THIS RIGHT!

Your friend has asked you to print a birthday invitation card. Write a program to accept the information entered by the user to print the card in the format below.

Invite Format

You are invited to Soha’s Birthday Party on 3rd May at 7pm

VENUE: Willow Springs, Gandhi Circle

Answer:

name = input("Enter your name : ")

date= input("Enter your date : ")

event = input("Enter event name : ")

time = int(input("Enter the time of the event : "))

addr = input("Enter venue address : ")

print("*"*16)

print("You are invited to")

print(name,"'s",event.upper())

print("on" ,date)

print("at",time,"pm")

print("VENUE",addr.lower())

print("*"*16)

String Formatting

Enter your name : Soha

Enter your date : 3rd May

Enter event name : Birthday Party

Enter the time of the event : 7 Enter venue address : Willow Springs, Gandhi Circle

You are invited to Soha's BIRTHDAY PARTY on 3rd May at 7 pm

VENUE willow springs, gandhi circle

%s reserves a place for the variables that hold the value to be inserted in the string.

Syntax: print("String %s " %variable_name)

act = "reset"

print("Every sunset is an opportunity to %s." %act)

Every sunset is an opportunity to reset.

Multiple strings can also be embedded within a single string using multiple %s operators. If there are multiple %s , the strings are replaced based on their order in the brackets.

fall = 7

stand = 8

str = 'times'

print('Fall %s %s and stand %s %s.' %(fall,str,stand,str))

Fall 7 times and stand 8 times.

Explanation

The f-String formatting

f-strings are another way to use and embed variables and expressions inside a string.

We start a string with the letter f followed by quotes, and the variables or expressions we want to embed within the quotes are enclosed within curly brackets {}.

Syntax: print(f"string {variable_name}.")

name = "Vanshita"

age = 19

print(f"Hello, {name}! You are {age}.")

The format() Function

Hello, Vanshita! You are 19.

To embed values using the format() function, we use curly brackets in the string where we want to replace values stored in variables. Then the variables are specified in the .format() function in the sequence we want them to be inserted in the string.

Syntax: "{} {}".format(value1, value2...) CODE

var1 = "You"

You

Matter!

Explanation

Solved Examples

Example 4.1

You are assigned a task to make a program to spread some joy amongst people who use your program.

Write a program to do the following:

(a) Get the name as input from the person and store it in a variable name.

(b) Using the %s and f-string embedding, produce the following output

Enter your name: Shnaya

Hey Shnaya! We learned string formatting today. Are you ready for some practice, Shnaya?

Answer: CODE

name=input("Enter your name: ") print("Hey %s! We learned string formatting today." %name) print(f"Are you ready for some practice, {name}?")

String Indexing

Every character in a string is given a number that is called an index. We can access each character of a string with help of these indices. The first character has index 0, the second character has index 1, and so on.

Syntax: string_name[index number] CODE

greeting = "Happy Journey!"

# H=0 a=1 p=2 p=3 y=4 white_space=5 J=6 o=7 u=8

print(greeting[8])

The index() Function

The index() function is used to get the index number of a particular character in a string.

If the character occurs more than once in the string, the index of the first occurrence of that character is returned.

Syntax: string.index(value, start, end)

#value - The character to search for #start (Optional): Index number to start the search from. Default is 0.

#end (Optional): Index number to end the search at. Default is to the end of the string.

str = "Crunchy Leaves"

Negative Indexing

Python numbers the characters of a string in two ways, forward and backward. While numbering backward, Python gives the characters a negative index starting from -1 for the last character in the string.

quote = 'Embrace the journey!'

print(quote[-1])

print(quote[-4])

Strings are Immutable

Python does not allow you to change any character in a string with help index. So we cannot change the value or a character within a string unless we reassign the entire string to the variable again.

msg = "Hey, Lio!"

msg[0] = "C"

print(msg)

String Slicing

TypeError: 'str' object does not support item assignment

In addition to indexing the strings, Python allows us to extract a part of a string. This extraction of strings is known as slicing and the extracted part of the string is known as a substring.

We slice a string by providing the starting index and 1 more than the ending index in square brackets [] after the variable.

Syntax: string_name[starting index:ending index]

s = "Embrace the journey!" print(s[2:7]) brace

Skipping Letters

Python can also skip letters in between while slicing. We use two colons for that.

Syntax:

String_name[start:end:step]

#If step is 3, python will print every third character

s = "Glorious journey!" print(s[4:16:2])

#python prints every second character

Slicing without Ending Index

By not specifying the ending index, Python automatically takes the last letter of the string as the endpoint.

Syntax: string_name[starting index:]

word = 'helipad'

print(word[2:]) lipad

Slicing without Starting Index

By not specifying a starting index, Python takes the start index of the first letter in the string.

Syntax: string_name[:ending index] CODE

The len() Function

word = 'helipad'

print(word[:6]) helipa

Python counts and returns the number of characters in a string using len() function.

Syntax: len(string_variable)

Solved Examples

Example 5.1

word = 'helipad'

print(len(word)) 7

Store your first name as a string in the variable first_name and your last name as a string in the variable last_name.

1. Print the length of the string.

2. Select the first letter of the variables first_name and last_name and store them in variables first_initial and last_initial respectively.

3. Now, print the name and the first and last initials on 2 separate lines.

OUTPUT

Enter your first name: Shreya

Enter your last name: Sharma

Entered name is: Shreya Sharma

Length of the name string is: 13

The first initial is: S

The last initial is: a

Answer:

first_name=input("Enter your first name: ")

last_name=input("Enter your last name: ") name=first_name+" "+last_name

print("Entered name is: ",name)

print("Length of the name string is: ",len(name))

first_initial=first_name[0]

print("The first initial is: ",first_initial)

last_initial=last_name[-1]

print("The last initial is: ",last_initial)

Example 5.2

The reversal of strings means the output shown would be a string from last to first. For example, take a string “Malayalam” and the reversal of it would be “malayalaM”.

1. Reverse the following string: ”Good Day”.

2. Now using string slicing, reverse each word separately and join them back together.

(i.e., Change ”Hello world” to “olleH dlrow”)

Good Day

Reverse of the entire string is: yaD dooG

Word 1: Good

Word 2: Day

Reverse of both words individually: dooG yaD

Answer: CODE

string_1="Good Day"

print(string_1)

string_1_rev = string_1[::-1]

print("Reverse of the entire string is:",string_1_rev)

word_1 = string_1[:4]

print("Word 1:",word_1)

word_2 = string_1[5:]

print("Word 2:",word_2)

string_2_rev = word_1[::-1]+" "+word_2[::-1]

print("Reverse of both words individually:",string_2_rev)

Find and Replace

The find() Function

The find() function returns the index of the first occurrence of the searched character or substring in a string.

The find() function returns -1 if the searched character or substring is not found within the string.

Syntax: string.find(<letter / substring to be searched>)

CODE

line = 'Kate on her skateboard!'

print(line.find('ate'))

#there are 2 ""ate"" substrings in the variable line, #but python shows the starting index of the first occurrence.

line = 'Kate on her skateboard!' print(line.find('Katie'))

#As 'Katie' is not present in the string, the output will be -1.

The replace() Function

The replace() function replaces a specified character or substring with another in a string. The part of the string you wish to replace and the new string to replace it with are specified inside the replace() function along with the number of times you want to replace.

Syntax:

string.replace('oldWord','newWord',count)

oldWord: word you want to replace

newWord: word you want to replace with

count: the number of times you want to replace oldWord with newWord

line = "bo bo bo! Merry Christmas!" print(line.replace('bo', 'ho', 2))

ho ho bo! Merry Christmas!

If a count is not specified python replaces all the occurrences.

line = "bo bo bo! Merry Christmas!" print(line.replace('bo', 'ho'))

Solved Examples

Example 6.1

ho ho ho! Merry Christmas!

You are given a string str1= “Hello , Have a nice day!”.

Take your name as an input and insert it between the string (using replace function) as shown below.

Hint: Replace the first space (“ “) with your name and spaces before it.

OUTPUT

Enter your name: Riya

Hello Riya, Have a nice day!

Answer:

str1= "Hello, Have a nice day!"

name = input("Enter your name: ")

str2 = str1.replace(' '," "+name,1) print(str2)

Example 6.2

We have a string str1=”plant trees, save earth”. You have to perform the following tasks in the specified sequence:

1. Replace all occurrences of the letter “e” with the letter “x”.

2. Find and print the index of the first and the last occurrence of the letter “x”.

3. Find and print the number of letters between the first and the last “x”. OUTPUT

The string after replacing e with x is: plant trxxs, savx xarth

Index of first x is : 8

Index of last x is: 18

Number of letters in between the first and the last x is: 9

Answer:

str1="plant trees, save earth" str1=str1.replace("e","x")

print('The string after replacing e with x is:',str1) firstx=str1.find("x")

str1_reverse=str1[::-1]

xtemp=str1_reverse.find("x")

lastx=len(str1_reverse)-1-xtemp

print('Index of first x is :',firstx)

print('Index of last x is:',lastx)

no_of_letters=lastx-firstx-1

print('Number of letters in between the first and the last x is:',no_of_letters)

Decision-making, as the name suggests, is making decisions based on certain conditions. To write these conditions we need to use comparison and logical operators.

Comparison Operators

Comparison operators compare the value on the left-hand side with the value on the right-hand side and return either True or False as a result of the comparison.

These operators are also known as relational operators. Below are the six comparison operators in Python.

== Equal to Returns True if both operands are equal x==y

!= Not Equal to Returns True if operands are not equal x!=y

> Greater than Returns True if left operand is greater than the right x>y

< Less than Returns True if left operand is less than the right x<y

>= Greater than or equal to Returns True if left operand is greater than or equal to the right x>=y

<= Less than or equal to Returns True if left operand is less than or equal to the right x<=y

# Using the inequality operator

print(3!=5)

print(2!=2)

# Using the greater than operator

print(1>3)

print(10>8)

# Using the less than operator

print(10<12)

print(10<9)

# Using the greater than or equal to operator

print(16>=16)

print(14>=15)

# Using the less than or equal to operator

print(16<=18)

print(15<=10)

Solved Examples

Example 1.1

Johnny has to check whether the number of balls in box A is equal to, less than or greater than the number of balls in box B. Box A contains 453 balls and box B contains 454 balls respectively. Using conditional statements print whether the situations are True or False.

OUTPUT

Are balls in box A equal to box B? False

Are balls in box A less than box B? True

Are balls in box A greater than box B? False

Answer:

box_A=453 box_B=454

cond1=box_A==box_B

print("Are balls in box A equal to box B?\n",cond1) cond2=box_A<box_B

print("Are balls in box A less than box B?\n",cond2) cond3=box_A>box_B

print("Are balls in box A greater than box B?\n",cond3)

Example 1.2

Joe’s mother gives him Rs. 350 and asks him to get some groceries from a nearby shop. He plans to buy tomatoes for Rs. 50, onions for Rs. 60, and a jar of Peanut Butter for Rs. 100.

(a) With the help of a conditional statement print True or False to help him find out if the money he has will be enough to buy the planned items or not.

(b) Joe plans to buy 2 more jars of Peanut butter with the remaining money. Help him decide if he has enough money for doing so.

OUTPUT

The total amount of money with Joe is: 350

The total bill will be: 210

Is the money adequate to buy groceries? True

The remaining amount left with Joe is: 140 Can Joe buy 2 more jars of Peanut butter?

False

Answer:

price_tomato=50

price_onion=60

price_butter=100

total_money=350

print("The total money with Joe is: ",total_money) total_bill=price_tomato+price_onion+price_butter

print("The total bill will be: ",total_bill)

cond=total_money>total_bill

print("Is the money adequate to buy groceries?\n",cond)

remaining_money = total_money - total_bill

print("The remaining amount left with Joe is: ",remaining_money)

cond2=remaining_money>(price_butter*2)

print("Can Joe buy 2 more jars of Peanut butter?\n",cond2)

Logical Operators

Logical operators are used to compare two or more conditions. These conditions can be formed using the comparison operators. We get a boolean value (True or False) as output after comparing these conditions.

The logical operators include “and” and “or”.

The and Operator

The and operator compares two conditional statements and returns True only if BOTH are true, else returns False in all other cases.

Syntax: Statement1 and Statement2

Following is the truth table for the AND operator:

Condition_1 Condition_2

and Condition_2

print(4<9 and 10==10) print(8>3 and 10==12)

The or Operator

The or operator compares two conditional statements and returns True if any one of the statements is true. It returns False if both conditional statements are false.

Syntax: Statement1 or Statement2

Condition_1 Condition_2

Condition_1 or Condition_2 TRUE TRUE TRUE TRUE FALSE TRUE FALSE TRUE TRUE FALSE FALSE FALSE

Multiple and/or Operators

We can form complex conditional statements in Python using multiple and/ or operators. In such cases where we have multiple and/or conditional statements, and has precedence over or. (i.e., the conditions with and are solved first and then the conditions with or are solved)

Syntax:

Statement1 or Statement2 and Statement3

#First we solve the AND operator, and then the OR

print(4>7 or 5==5 and 7>5)

Solved Examples

Example 2.1

David needs to select students for his upcoming project based on two criteria. The students should have 60% in their academics, and they should have a score of 7 in their analytical tests.

Now, Ray has a score of 65% in his academics and 8.5 in analytical tests. Similarly, Joe has a score of 55% in his academics and 8 in analytical tests.

So display True or False based on the condition each for Ray and Joe whether they pass David’s criteria or not.

OUTPUT

Ray's scores:

Academics: 65%

Analytical test: 8.5

Does Ray meet David's criteria? True

Joe's scores:

Academics: 55%

Analytical test: 8

Does Ray meet David's criteria? False

Answer:

ray_academics=65

ray_analytical=8.5

print(f"Ray's scores:\nAcademics: {ray_academics}%\nAnalytical test: {ray_analytical}")

ray_condition = ray_academics>=60 and ray_analytical>=7

print("Does Ray meet David's criteria?\n",ray_condition)

joe_academics=55 joe_analytical=8

print(f"Joe's scores:\nAcademics: {joe_academics}%\nAnalytical test: {joe_analytical}")

joe_condition = joe_academics>=60 and joe_analytical>=7 print("Does Ray meet David's criteria?\n",joe_condition)

Example 2.2

Ben is the captain of the school’s football team. He needs defensive players who are tall and strong and offensive wingers who are short and agile.

For defense, he needs players taller than 6 feet and with a weight of more than 68 kg.

For offense, he needs players shorter than 5.5 feet and with a weight of less than 57 kg.

Take your height and weight as float inputs, and with the help of Comparison and Logical operators, print True or False for the combined condition.

OUTPUT

Enter your height in feet: 5

Enter your weight in Kg: 55

Do you satisfy any of Ben's criteria for the football team?

Answer:

CODE

height=float(input("Enter your height in feet: "))

weight=float(input("Enter your weight in Kg: "))

condition = (height>6 and weight>68) or (height<5.5 and weight<57)

print("Do you qualify any of Ben's criteria for the football team?\n ",condition)

Indentation and Block

Indentation is a fixed number of spaces added at the beginning of the code, grouping a set of statements into a particular block of code. So Python runs a particular block of code at a time.

Below you can see how the spaces or Indentation divides the code into various blocks of code.

Flowchart and its Components

Flowchart is a diagram and a graphical representation of an algorithm or program.

It is the blueprint of the program and it shows steps in sequential order.

Certain shapes are used to draw flowcharts, and these shapes have the meaning as follows:

Purpose Represents a start or end point

Represents the connection between two shapes and the flow of program Represents input or output

Conditional Statement

Represents the process or block of code

Represents the decision or conditional statement (Output is usually True or False)

A conditional statement is a statement that tests a criterion and performs the defined action if it becomes true.

The if-else Statement

The if-else statement in Python is the most simple decision-making statement. It is used to decide if a certain condition or set of conditions is True or not.

If the condition after the “if” keyword is True, the code block after the if condition is executed, and if the condition is False, the code block after the “else” keyword is executed.

It is not necessary to have another condition.

Syntax: if condition_1:

#Statements to execute if condition_1 becomes True else:

#Statements to execute if condition_1 becomes False

age = 21

if age >= 18:

print("Eligible to vote.")

else: print("Too young to vote!")

Flowchart

Eligible to vote.

Nested if-else Statements

Nesting is the process of adding an if-else statement within another if-else. This will help us evaluate the second condition only when the first condition is True.

The first if statement is commonly called “outer if” and the block within it is called “nested / inner if”.

Syntax:

if condition_1:

if condition_2:

Statement_A

else:

Statement_B

else:

if condition_3:

Statement_C

else:

CODE

age=10

height=160

if age >= 10:

if height > 150:

Statement_D

OUTPUT

You get a roller-coaster!

print('You get a roller-coaster!') else:

else:

print('You get water rides!')

print('Sorry, no rides for you!')

The elif Statement

In situations where we have multiple conditions to evaluate the elif statement is used. This in simple terms means “else if”. The elif statement lets you add more than one conditional statement after the if statement or between the if and else statements in the program.

Flowchart

In multiple elif conditions, Python checks for the next one if the previous ones are False.

Syntax: if condition_1:

Statement_1

elif condition_2:

Statement_2

elif condition_3:

Statement_3 .. .. ..

else:

age=10

height=160

if age >= 10 and height > 150: print('You get a roller-coaster!')

elif age >= 10 and height <= 150: print('You get water rides!')

else: print('Sorry, no rides for you!')

Flowchart

You get a roller-coaster!

Solved Examples

Example 3.1

Take a number as an input from the user and write a program to check whether the given number is a positive number or a negative number. Also, take another number as a reference in the variable ref_number and display if the input number is on the left or right-hand side of the reference number when put on the number line.

OUTPUT

Enter a number: -5.2

The input number -5.2 is negative

Enter a reference number: -9 -5.2 is on the right-hand side of the number -9.0

Answer:

num=float(input("Enter a number: ")) if num>0:

print(f"The input number {num} is positive")

else:

print(f"The input number {num} is negative")

ref_number = float(input("Enter a reference number: ")) if num>ref_number:

print(f"{num} is on the right-hand side of the number {ref_ number}")

else:

print(f"{num} is on the left-hand side of the number {ref_ number}")

Example 3.2

Write a program to get today’s day as the input and check if it is a “weekend” or a “weekday”.

If it is a day from the weekend, check if the next day is a weekend or a weekday.

OUTPUT

Enter today's Day: Monday

Monday is a weekday.

Enter today's Day: Saturday Saturday is a weekend.

Next day is Sunday, it is the weekend.

Answer:

CODE

current_day = input("Enter today's Day: ")

if current_day.lower()=="Monday" or current_day.lower()=="Tuesday" or current_day.lower()=="wednesday" or current_day.lower()=="Thursday" or current_day.lower()=="Friday":

print(f"{current_day} is a weekday.")

elif current_day.lower()=="Saturday":

print(f"{current_day} is a weekend.")

print("Next day is Sunday, it is the weekend.")

elif current_day.lower() == "sunday":

print(f"{current_day} is a weekend.")

print("Next day is Monday, it is a weekday.")

Practice Problems

1. Write a program to print a bill as given below using sep.

2. Below are the marks of a student named Max in different subjects. Store the scores in variables to print the total and average.

3. There are three trains. Train 1 covers 25 km per hour. Train 2 covers 50 km per hour. Train 3 covers 80km per hour. How far do the trains go in 2.5 hours?

OUTPUT

Train 1 covers 62.5km

Train 2 covers 125km

Train 3 covers 200km

4. In a quiz competition, for each correct answer you get 2 points and for each incorrect answer 1 point is deducted. There are 12 questions in total. What are the maximum and minimum marks that you can score in the competition? Convert those marks into the string and the boolean values and print them as well.

OUTPUT

Maximum marks=24

Float value= 24.0

Minimum marks=-12

Float Value= -12.0

5. Create a program that uses the input of the game’s name. Display a boolean value to see whether the entered name is lowercase or not. Also, it would look messy to store the game names if everyone used a different case so, convert the input to uppercase.

OUTPUT

Enter a game you like to play: Football

Entered Game name is: FOOTBALL

The input is in lowercase: False

6. It is the start of the school year and you are at a notebook store. The shopkeeper asks your help to print the bill. The rate of the note books are as follows:

Print the total bill of a customer who purchases 3 blank, 4 ruled, and 1 grids notebooks.

7. Input a sequence of vegetables in a single string.

For example veggies = “Carrot Radish Tomato Beans Okra”

You have to display this in a vertical manner using the replace function and the newline character.

OUTPUT

Enter the name of vegetables : Carrot Radish Tomato Beans Okra

The list with each item on a new line as follows: Carrot Radish Tomato Beans Okra

8. Write a program to take a year as input from the user and calculate whether the year is a leap year or not.

Hint: Leap year is the year which is divisible by 4 and not by 100 or which is directly divisible by 400.

OUTPUT

Enter a year: 2004

The year 2004 is a leap year

Enter a year: 1999

The year 1999 is not a leap year

Loops

While programming, we will often come across situations where we need to use a piece of code over and over again. However, writing the same line of code multiple times does not make sense. This is where loops come in handy. Loops help us repeat a set of instructions again and again until a particular condition remains True. As soon as the condition becomes False, the loop stops.

Process of a Loop

Python provides mainly two types of loops, the While loop and the For loop. But the steps remain loosely the same as below.

A looping process has mainly 4 steps:

1. Creating a condition variable and storing an initial value in it

2. Providing a test condition that runs the loop (This should be carefully stated in order to run the loop for a desired number of times)

Flowchart

3. A set of instructions inside the loop

4. Updating the value of the condition variable

Infinite Loop

In some cases, the body of the loop gets executed over and over as the test condition never becomes false, and the execution never stops. Such a loop is called an Infinite loop.

The while Loop

The simplest looping statement is the while statement. It allows a programmer to repeat a set of instructions when the condition is evaluated as True, hence it is also known as a conditional loop.

It verifies the condition before executing the loop. The code inside the while loop is repeated as long as the given condition remains True.

A while loop can be written using:

(a) The while keyword

(b) A condition which is either True or False

(c) A block of code, which is nothing but the set of instructions that is supposed to be repeated

Syntax: while condition:

Statement 1

Statement 2 ... ...

(Incrementing the value if required)

Proper indentation needs to be provided for the block of code present inside the while loop. It is also called the body of the loop.

Explanation

Here, count is the condition variable, which starts with 1, and when Python checks the condition (count < 6), it comes out to be True. So, the loop starts. In line 3, the value of count is displayed. Then in line 4, i is increased by 1 (count = count + 1 = 1 + 1 = 2). After that, Python checks the condition again. As 2 < 6 is True, the loop runs again. This continues till the value of count is less than 6. When count becomes 6, the condition becomes False, and the loop stops.

The for Loop

The for loop is another looping statement. It is also known as a counting loop because we can use it to count up to a number or go through a sequence of values.

We use a variable to create the for loop called the loop variable.

The two ways to create a for loop:

1. With the range() function

2. Without using the range() function.

Using range() Function

Using range() function, we can specify a starting number and an ending number. So, the for loop will start from the starting number and continue up to (ending number - 1), increasing the number by 1 after each loop.

Syntax:

for loop_variable in range(start, end, steps):

<statements>

#the loop runs from start to end-1

start Optional. An integer number specifying at which position to start. If the start number is not specified, Python takes 0 by default.

stop Required. An integer number specifying at which position to stop (not included).

step Optional. An integer number specifying by what value to increase the value of loop variable. By default Python increases the value by 1.

Explanation

Here, the starting number is 0 and the ending number is 5. So, the for loop starts counting from 0 and continues till (ending number - 1) which is 4. And after each loop, the value of 1 increases by 1.

Without Using The range() Function

Without using the range function, a for loop can iterate over letters in a string, values in a list or a dictionary as well.

Syntax: for loop_variable in string_variable: <statements>

Explanation

Here the loop starts with the first letter, i.e., letter = ‘a’. And in each loop, the value of the variable changes to the next letter in the string. So in the second loop, letter = ‘d’, in the third loop, letter = ‘v’, and so on. It continues up to the last letter in the string.

The for versus while Loop

The for Loop

In for loop, we initialise, test and update the loop variable during writing a loop in one single line, whereas the while loop requires more lines.

For loop is also called a counting loop since it counts up to a number. for i in range(start, stop, increment):

//step1 //step2

The while Loop

In a while loop, the condition is tested first and the loop gets executed when the condition is met. In case, if we forget to update the loop variable, there are chances we may end up in an infinite loop which doesn’t happen in the case of for loop.

While loop is also called a conditional loop because it has a condition.

i=1

while(i<=10):

//step1 //step2

Nested Loop

A nested loop is a loop inside another loop. The first loop we start off with is called the outer loop. All the loops that are written inside the outer loop are called inner loops. The outer loop can contain more than one inner loop. The inner or outer loop can be any type, such as a while loop or a for loop.

The entire “inner loop” gets executed every time the “outer loop” runs.

If the outer loop runs 5 times, and the inner loop runs 10 times. Then for the 1st iteration of the outer loop, the inner loop will run 10 times, for the 2nd iteration of the outer loop, the inner loop will run 10 times, and so on.

So in total, the inner loop will run 5 (outer loop count) * 10 (inner loop count) = 50.

Nested for Loop

rows = 6 for num in range(rows): for i in range(num): print(num, end=" ") # print

A while Loop Inside A for Loop

Nested while Loop

A for Loop Inside A while Loop

while i<6: for j in range(0,i): print(i,end="

The break and continue Statements

Loops run the same set of code for a defined number of times or until the test condition becomes False, but sometimes we might wish to stop the loop even before the test condition becomes False or skip an iteration.

In those cases, we can use the break and continue statements.

The break Statement

The break keyword is used to break out / get out of the loop and execute the next statement.

Syntax:

while expression:

if condition: break

#breaks out of the loop

#executes statement outside the loop

word = input('Enter a word: ') for letter in word:

if letter in 'aeiou': print('Vowel found!') break

Explanation

Enter a word: Success Vowel found!

Here, the loop runs for all the letters in the word entered by a user. Inside the loop, Python checks the condition if the letter is a vowel or not (i.e. a, e, i, o, u). If the condition becomes True, Python runs the break statement in line 5, which forces it to stop the loop.

The continue Statement

The continue keyword is used to skip the execution of statements ahead in the loop. Python skips the statements after the continue keyword in the current iteration/cycle of the loop and does not stop the loop.

#skips next set of statements and starts with next loop

Explanation

Here, the for loop starts counting from 1. In each loop, it increases the value of num by 1, and when num is equal to 12, 15, or 19 (i.e. the condition in line 2) is True, Python runs the continue statement, which forces it to skip the lines below it. That is why the numbers 12, 15, and 19 are not displayed in the output.

Practice Problems:

1. Write a program to print the table to any number using a while loop.

2. Create a program to print multiples of a number in the range 1 to 100.

3. Write a program to calculate the sum of the first 10 natural numbers using a for loop.

4. Write a program to display following pattern using nested loop:

5. Print all the numbers between 1 to 50 except the multiples of 5 using the continue statement.

In our day-to-day routine, we use a lot of machines for various purposes such as washing machine, oven, fan, tubelight, air conditioner, stove, chimney and a lot more. All these machines serve some specific purposes.

Let us take the example of a vending machine. A vending machine is an automated machine used to purchase items such as snacks, juices and soft drinks.

To purchase an item from a vending machine:

● Use buttons or the digital panel provided to select items and pay for them.

● Then, collect the items from the dispenser once the payment is done.

A vending machine does the above tasks every time it is used, which is an example of a function.

Every day, we repeat certain tasks over and over again. Therefore, if we automate them—that is, if we create them only once and reuse them as necessary—it becomes simple.

In programming, we come across situations where we need to repeat a particular set of lines for a task. So, instead of rewriting it, wouldn’t it be better to write it once and then use it as many times as we want without repeating ourselves?

But we can solve this with functions. We can create them once and call them whenever needed.

Function

A function is a reusable block of code which can be used over and over again to perform a particular task.

The following are the two main categories of function:

1. Built-in functions

2. User-defined function

Built-in Functions: The functions that are already available in the library of python for our usage are known as built-in functions. These functions can be used anywhere in the program just by importing the specific library.

For example : print("Hello World!")

User-defined function : The functions that we create for achieving a particular task are known as user-defined functions. For defining a function in Python we use the def keyword followed by the function name.

For example : def my_function():

print("Hello, this is my first function");

Structure of a Function

Syntax for defining a function: In Python a user-defined function can be defined using def keyword. A function can have n number of statements.

Syntax: def function_name(): Statement1 ; Statement2; ….. ….. Statement n;

Example: def my_function: print("Hello! This is my first function");

Calling a Function: A function can be called by simply using the function name.

Example: for calling the above defined function my_function();

Output: Hello! This is my first function

Arguments and Parameters

Parameters are the variables that we pass while defining a user-defined function.

Whereas arguments are the variables that we pass while calling a function.

Example :

Output: 7

Explanation: Here, the parameters are x and y, and the arguments are 3 and 4 for the respective parameters, i.e., x = 3 and y = 4.

Types of Arguments

Python functions can have two types of arguments:

1. Positional arguments

2. Keyword arguments

Positional Arguments

Positional arguments need to be passed in the same order used in function definition.

Example:

Output: Daisy Brown

Explanation: Here, Daisy and Brown will be taken by the parameters according to their position.

first_name = Daisy

last_name = Brown

Keyword Arguments

Keyword arguments are the arguments that are preceded by a keyword and an equal to sign (i.e. Key = Value), here the order of the arguments does not matter as the values are being assigned explicitly.

Example:

def name (first_name , last_name):

print (first_name + last_name);

name (last_name = “Brown”, first_name = “Daisy”);

Output: Daisy Brown

Explanation: Here, the arguments are passed with their respective keywords, such as last_name = Brown and first_name = Daisy.

Return Value

A function can return a value as a result , which makes it generalised. To get a function to return a value we can use the ‘return’ statement.

These functions can also be used to perform calculations or transformations on the input data and return the result. It makes the code more readable and maintainable. Such functions can be used in almost any programming scenario where a specific task needs to be performed repeatedly or where a calculation or data processing needs to be done.

Example:

Output: 16

Explanation: Here x = 4, So the function will return (4*4) i.e. 16.

You can even catch the result returned by the function in a variable.

Example:

Output: 16

Explanation: Here the variable square is catching the result from the function number_square and then printing the result.

Recursion

Recursion is a common programming and mathematical concept. When a function calls itself is known as recursion. Recursion is a very efficient way to write a program.

The above image shows the working of a function recurse() which is calling itself in its definition.

Example:

Output: The factorial of 3 is 6.

Explanation: Here the factorial() is a recursive function created to calculate the factorial of a number.

When we call this function with a positive integer it will recursively call itself by decreasing the number.

Our recursion ends when the number reduces to 1. This is called the base condition.

Every recursive function must have a base condition to stop the recursion otherwise it will run infinitely.

Practice Questions:

1. Create a program to find the product of two numbers using a function with parameters.

2. Create a program to find if a number is prime or not using a function that returns the result.

3. Create a program that counts down from a specified number to zero using a recursive function.

4. Create a program to generate a fibonacci sequence using a recursion function.

5. Create a program to calculate the square of any number using a function that accepts parameters and returns the result.

Chapter 4 Lists

Lists are used to store multiple values in a single variable. They are one of the most used data types that allow us to work with multiple values at once. To create a list, we store multiple values in between the square brackets. Each value is given a number called an index and the index starts from 0. The values inside the loop can be accessed using these index numbers.

Example: num_list = [1, 2, 3, 4, 5, 9, 6, 2]

Features of Lists

● They are ordered, i.e., Python always maintains the order in which you store the values in the list

● They have no fixed size or limit

● We can modify a list, i.e., we can add, update, or delete any value from a list

● The values in a list can be of the same or different data types

Syntax:

list_name = [value1,value2,value3,value4,................,valuen]

animals = ["lion", "tiger", "horse","cat","dog","rabbit"] print(animals)

List Traversal

List Indexing

['lion', 'tiger', 'horse', 'cat', 'dog', 'rabbit']

Each element in a list can be accessed by its index number.

Indexing like strings can happen in two ways,

● Positive indexing (Used to access elements in forward direction)

● Negative indexing (Used to access elements in backward direction)

animals = ["lion", "tiger", "horse","cat","dog","rabbit"] print(animals[0]) print(animals[-1])

List Slicing

lion rabbit

Lists can be sliced again in the same way as strings. We get a slice of the list or sublist by giving the starting index, ending index and an index jump. Python starts slicing the list at the starting index and continues till (ending index - 1). We use a simple slicing operator (:) to slice a list.

Syntax:

List_name[starting_index : ending_index : index_jump]

where,

starting_index: Starting point for slicing.

ending_index: Ending point for slicing. Python slices the list till (ending_ index - 1)

index_jump: Number of elements skipped. If the value is 2, then Python skips one value after slicing an index number. If the value is 3, then Python skips 2 values after slicing an index number.

CODE OUTPUT

NOTE: The default value for index_jump is 1. If we don't specify index_jump value , 1 will be considered as the value for index_jump. In that case, Python does not skip any value in the middle. CODE

vowels = ['a', 'e', 'i', 'o', 'u'] print(vowels[2:5])

Explanation

['i', 'o', 'u']

Here, Python starts slicing the list at index number 2 (i.e., ‘i’) and continues till the index number 4 (i.e., ‘u’) .

vowels = ['a', 'e', 'i', 'o', 'u'] print(vowels[1:5:2])

Explanation

['e', 'o']

Here, Python starts slicing the list at index number 1 (i.e. ‘e’). As the value of index_jump is 2 here, Python skips one value after index 1 and jumps to index 3 (i.e. ‘o’). Then, it skips index 4 and jumps to index 5, which does not exist in the list, so Python stops there. Hence, the final output is [‘e’, ‘o’].

Looping in List

Lists can be iterated over by using a loop in the same way as strings. Each time the looping variable holds the value of each element in the list.

Syntax:

list_name=[item1,item2,item3,...] for item in list_name: print(item)

vowels = ['a', 'e', 'i', 'o', 'u'] for letter in vowels: print(letter)

Occurrence of an Element in List

To check if a specific element is present in a list or not, we can use the in keyword to form the condition. This condition will return True if the element is in the list and False if it is not in the list.

Syntax:

list_name=[item1,item2,item3,...] print(item_name in list_name)

vowels = ['a', 'e', 'i', 'o', 'u'] print('b' in vowels)

Explanation

As ‘b’ is not present in the list, Python displays False as output.

Lists are mutable

In lists, items can be changed by specifying their index. We just need to use the assignment operator to assign the value on the right at the specified index. This cannot be done in strings.

Syntax:

list_name[index] = value

numbers = [1,2,3,4,5] numbers[0] = "111" print(numbers)

Adding and Repeating List

Joining/Adding Lists

In Python, we can join two or more lists into one list. We can use the + operator to merge the contents of two lists into a new list.

list_1 = [1, 2]

list_2 = [3, 4]

print(list_1 + list_2)

Repeating Lists

The elements inside a list can be repeated within the list multiple times using the * symbol. All the elements in a list are repeated in the same order for the number of times mentioned after the * operator. We can only use an integer value after the * symbol. Using a float value will show an error.

Syntax: list2 = list1 * integer_number

list_1 = [1, 2, 3]

print(list_1 * 2)

nested_list = [1, 2, [3, 4]]

print(nested_list * 2)

Nested Lists

A list can contain another list as a value which in turn can contain sublists themselves, and so on. This method of building a list within another list is known as nesting of lists. These inner lists are called "sub-lists".

Syntax:

list_name = [item1, [item2_1, item2_2, item2_3], item3, item4]

Here, [item2_1, item2_2, item2_3] is the nested list.

Indexing in Nested List

If we want an item within the nested list or sublist of the list, we access it using the following 2 indices.

1. We first specify the index of the sublist

2. We then specify the index of the element inside the sublist that we want to access

Syntax:

list_name[index of sublist containing the item][index of the item]

= [1, 2, [3, 4]] print(num_list[2][0])

Explanation

Here, num_list[2] first accesses the sublist, i.e., [3, 4]. Then, num_list[2][0] accesses the first value inside the sublist, i.e., 3.

= [1, 2, [3, [4, 5]]] print(list_num[2][1][1])

Explanation

Here, num_list[2] first accesses the sublist, i.e., [3, [4, 5]]. Then, num_list[2][1] accesses the second value inside the sublist, i.e., [4, 5]. Finally, num_list[2][1][1] accesses the second value inside the innermost sublist, i.e., 5.

List Operations

The len() Function

The len() function is used to get the number of elements in a list.

Syntax: len(list_name)

The append() Method

The append() method can be used to add elements to the end of the list.

Syntax: list.append(element)

CODE

list_1 = ['Mathematics', 'chemistry', 1997, 2000]

list_1.append(20544)

print(list_1)

The insert() Method

['Mathematics', 'chemistry', 1997, 2000, 20544]

The insert() method helps us to insert an element at a specific index or location in a list. We specify the position of the index at which we want to insert the element and then the element separated by a comma.

Syntax: list.insert(position_index, element) CODE

List = ['Mathematics', 'chemistry', 1997, 2000]

List.insert(2,10087)

print(List)

Explanation

Here, Python inserts 10087 at index 2 inside the list.

The remove() Method

['Mathematics', 'chemistry', 10087, 1997, 2000]

The remove() method removes the specified item from a list. We specify the element we wish to remove from the list in the brackets. The method removes the 1st occurrence of the element from the list.

Syntax: list.remove(element)

Explanation

Here, Python removes the first 3 from the list.

The del Keyword

The del keyword removes the element at a specified index and can also delete the list completely.

Syntax: del list[index]

Minimum min() and Maximum max() item in a list

The min() method returns the minimum value from the list. In case of numbers, the number with least value is returned, in case of strings, the string with the lowest alphabet is returned.

Syntax: min(List)

The max() method returns the maximum value from the list. Same as min(), in case of strings, the string with the greatest alphabet is returned.

Syntax: max(List)

Sum of Items in a List - sum()

The sum() function returns the sum of all items in a list.

Syntax: sum(List)

Practice Problems:

1. Write a program to check whether a number exists in a list or not?

2. Write a program to calculate the sum and average of all numbers in a list.

3. Write a program to count even and odd numbers in a list.

4. Write a program to count occurance of a number in a list.

5. Create a list of marks in mathematics of 10 students and display maximum and minimum marks.

Dictionary is a data type that is used to store data in key:value pairs. It is an unordered collection of elements. A dictionary can be created by placing a sequence of elements within curly {} brackets. A dictionary can be created by placing a sequence of elements within curly {} brackets, separated by ‘comma’.

Example :

dict = { 'Name': 'Daisy', 'Age': 12, 'Grade': 7 }

Features of a Dictionary:

● Each element is accessed through its key.

● Values of a dictionary are mutable or changeable.

● Each key in the dictionary must be unique as it does not allow duplicate data.

NOTE: Dictionary keys are case sensitive, the same name but different cases will be treated distinctly.

Example:

dict = { 'a': 1, 'A': 2 }

Here a and A will be considered unique.

Accessing a Dictionary

The name of the dictionary can be used to access all of its elements and the key name is used to access a particular element of the dictionary.

dict = { 'Name': 'Daisy', 'Age': 12 , 'Grade': 7 }

print(dict)

{'Name': 'Daisy', 'Age': 12, 'Grade': 7}

dict = { 'Name': 'Daisy', 'Age': 12, 'Grade': 7 }

print(dict['Name'])

dict = { 'Name': 'Daisy', 'Age': 12 , 'Grade': 7 }

print(dict['Age'])

Updating a Dictionary

You can update a dictionary by :

● Adding a new item in it using key:value pair

● Modifying the existing item

● Deleting any item from it

CODE OUTPUT

dict = { 'Name': 'Daisy', 'Age': 12, 'Grade': 7

# Adding a new item dict['LastName'] = 'Brown' print(dict)

{ 'Name': 'Daisy', 'Age': 12, 'Grade': 7, 'LastName': 'Brown'}

CODE OUTPUT

dict = { 'Name': 'Daisy', 'Age': 12, 'Grade': 7

# Updating/Modifying an existing item dict['Grade'] = 8 print(dict)

{ 'Name': 'Daisy', 'Age': 12, 'Grade': 8, 'LastName': 'Brown'}

Deleting an Element from a Dictionary

The del keyword can be used to delete a particular item from the dictionary. You can even delete the entire dictionary using the same.

CODE OUTPUT

dict = { 'Name': 'Daisy', 'Age': 12, 'Grade': 7, 'LastName': 'Brown'

# Deleting an item del dict['LastName'] print(dict)

{'Name': 'Daisy', 'Age': 12, 'Grade': 7}

dict = { 'Name': 'Daisy', 'Age': 12, 'Grade': 7, 'LastName': 'Brown' }

# Deleting the entire dictionary del dict print(dict)

<class

Note: you can use clear() to remove all the entries from the dictionary.

Example: dict.clear();

Properties of Dictionary

Dictionary is a commonly used data type in Python to store multiple values using the key: value pair.

Although before using the dictionary you must understand the properties of dictionary keys:

1. No duplicate keys allowed: More than one entry for a particular key is not allowed. In such cases the last assignment for the key will be considered .

dict = { 'Name': 'Daisy', 'Age': 12, 'Grade': 7, 'Name': 'John' }

print(dict['Name'])

Explanation: Here the key ‘Name’ was repeated so the last assignment i.e. ‘John’ will be considered.

2. The values of a dictionary are mutable, whereas keys are not. That is why lists are not allowed as keys of a dictionary. Because lists are mutable.

dict = {

CODE OUTPUT

TypeError: unhashable type: 'list'

'Name': 'Daisy', 'Age': 12, ['Grade']:7

print(dict)

Nested Dictionary

A dictionary can contain dictionaries, this is called a nested dictionary.

Syntax:

nested_dict = {

'dict1' : {'key_A' : 'value_A'}, 'dict2' : {'key_B' : 'value_B'}

students = { 1: {

"Name": "Daisy", "Grade": 7, "Roll_number": 5 }, 2: {

"Name": "John", "Grade": 7, "Roll_number": 10

print(students)

{1: {'Name': 'Daisy', 'Grade': 7, 'Roll_number': 5}, 2: {'Name': 'John', 'Grade': 7, 'Roll_ number': 10}}

CODE OUTPUT

details = {

'Name': 'Daisy', 'Age': 12, 'Marks': { 'Eng': 89, 'Math': 95, 'Computer': 98 }

Dictionary Methods

{'Name': 'Daisy', 'Age': 12, 'Marks': {'Eng': 89, 'Math': 95, 'Computer': 98}}

Python has various methods to work with dictionaries. Following are the methods of Python dictionary:

Method Description Syntax clear() Removes all the items from the dictionary.

copy() Returns a copy of the dictionary.

dict.clear()

dict.copy()

fromkeys() Creates a dictionary from a given sequence. dict. fromkeys(sequence,value) get() Returns the value of a given key.

items() Returns a list with all the keys and values.

keys() Returns all the keys of the dictionary.

values() Returns all the values of the dictionary.

dict.get(key,default = None)

dict.items()

dict.keys()

dict.values()

Method Description Syntax

setdefault() Inserts a key with default value to the dictionary.

update() Updates an existing dictionary item.

pop() Removes and returns the specified element from the dictionary.

popitem() Removes the last inserted key-value pair.

sort() Sorts the dictionary in reference with keys.

len() Shows the total number of items in the dictionary.

Practice Questions:

dict.setdefault(key, default_ value)

dict.update([other])

dict.pop(key)

dict.popitem()

dict.sort()

len(dict)

1. Create a dictionary to store prices of fruit and display the prices of all fruit.

2. Create a Python program to store details of a student (Name, Grade, Address, PhoneNumber, Favourite_Subject) using a dictionary data type and display all the values.

3. Create a phone book program using a nested dictionary and store details of your 3 friends and display them.

4. Create a dictionary to store your marks of all your subjects and display them.

5. Create a nested dictionary to store the capital and currency of any 5 countries.

Coding Challenge

Create a dictionary that stores student details. Add new keys in that dictionary by taking inputs from the user.

About this book

This coding book is supplementary to the main “Mel n Conji” content book. This book represents a 21st-century approach to learning coding concepts and developing computational thinking and problem-solving skills. To prepare students for the digital age, the curriculum is interwoven with well-thought-out concept graduation with real-life examples and practice problems.

Special features

• Illustrative approach: Concepts in coding and computer science are delivered through pictorial representations and learner-friendly approaches.

• Learning through real-life examples: Age-appropriate examples that enable learners to relate to the concept and learn about the unknown from the known.

• Extensive practice: Multiple practice scenarios to reinforce learnings.

• Coding Challenges: Includes projects through which learners can demonstrate their learning outcomes in coding and computer science.

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