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If-Else Statements in Python

If-else statements are fundamental building blocks for decision-making in Python programs. They allow you to control the flow of your code based on whether a certain condition is True or False.

Basic Structure :

The basic syntax of an if-else statement is:



										if condition:

										# code to execute if the condition is True

										else:

										# code to execute if the condition is False

The if keyword is followed by a condition that is evaluated as True or False.

If the condition is True, the indented code block after the if statement is executed.

If the condition is False, the indented code block after the else statement (if present) is executed.

Python code

													
													# Example: Checking for Pass/Fail

													marks = int(input("Enter your marks: "))
													
													if marks >= 60:
													
													print("Congratulations! You passed.")
													
													else:
													
													print("You didn't pass. Please try again next time.")

This program asks the user for their marks. It then uses an if statement to check if the marks are greater than or equal to 60 (assuming the passing mark). If the condition is True, the "Congratulations" message is printed. Otherwise, the "You didn't pass" message is printed.

Key Points :

The condition can be any expression that evaluates to True or False. Common comparisons include == (equal to), != (not equal to), < (less than),> (greater than), <= (less than or equal to), and>= (greater than or equal to).

You can have multiple lines of code indented within the if and else blocks

If the condition is False, and there's no else block, no code is executed after the if statement.

Basic Examples

Python code

													
													#1. Example: Grade Calculation

													marks = int(input("Enter your marks: ")) 

													if marks >= 90: 

													print("Excellent! You got an A.") 

													elif marks >= 80: 

													print("Great work! You got a B.") 

													elif marks >= 70: 

													print("Well done! You got a C.") 

													else: 

													print("Keep practicing! You got a D or F.")

Python code

													
													#2. What is the pricing structure for parcel deliveries between
													Delhi and Kolkata, or vice versa, offered by 'Atul Transport
													Company'? The charges are as follows:

													Up to 10 kg: Rs. 20 per kg,
													For the next 20 kg: Rs. 10 per kg,
													For the subsequent 20 kg: Rs. 8 per kg,
													For parcels weighing more than 50 kg: Rs. 5 per kg.
													
													r = int(input("weight of the parcel : ")) 

													if r <= 10: 

														u1 = (r * 20) 

														print(f"the charge for parcel {u1}") 

														elif r <= 30: 

															u2 = (r * 10) 

															print(f"the charge for parcel {u2}") 

															elif r <= 50: 

																u3 = (r * 8) 

																print(f"the charge for parcel {u3}") 

																elif r > 50: 

																u4 = (r * 5) 

																print(f"the charge for parcel {u4}") 

																else: 

																print("invalid unit")

This program uses nested if and elif (else if) statements to assign grades based on the marks. The elif statements are checked only if the previous if conditions are False.

Practice Exercises:

1. Write a program that asks the user for a number and checks if it's positive, negative, or zero.

2. Write a program that asks the user for the day of the week (as a number, e.g., 1 for Monday) and prints the corresponding day name.

By mastering if-else statements, you can add logic and decision-making capabilities to your Python programs, making them more versatile and interactive.

If-Else Statements in Python

Basic Structure :

Key Points :

Basic Examples

Practice Exercises:

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