Python – Conditional Statements

Conditional statements in Python allow you to execute certain pieces of code based on whether a condition is true or false. Here are the main types of conditional statements in Python:

if Statement

The if statement is used to execute a block of code if a specified condition is true.

Syntax:

if condition:
    # code to execute if condition is true

Example:

age = 18
if age >= 18:
    print("You are eligible to vote.")

In this example, the message “You are eligible to vote.” is printed because the condition age >= 18 is true.

elif Statement

The elif (short for “else if”) statement allows you to check multiple conditions, one after another.

Syntax:

if condition1:
    # code to execute if condition1 is true
elif condition2:
    # code to execute if condition2 is true
elif condition3:
    # code to execute if condition3 is true
...
else:
    # code to execute if all conditions are false

Example:

score = 75

if score >= 90:
    print("Grade: A")
elif score >= 80:
    print("Grade: B")
elif score >= 70:
    print("Grade: C")
elif score >= 60:
    print("Grade: D")
else:
    print("Grade: F")

In this example, the output is “Grade: C” because the condition score >= 70 is true.

else Statement

The else statement is used to execute a block of code if none of the preceding conditions are true.

Syntax:

if condition:
    # code to execute if condition is true
else:
    # code to execute if condition is false

Example:

is_raining = False

if is_raining:
    print("Take an umbrella.")
else:
    print("No need for an umbrella.")

In this example, the message “No need for an umbrella.” is printed because the condition is_raining is false.

Combining if, elif, and else

You can combine if, elif, and else statements to handle multiple conditions in a more complex decision-making structure.

Example:

temperature = 30

if temperature > 35:
    print("It's extremely hot outside!")
elif temperature > 25:
    print("It's hot outside!")
elif temperature > 15:
    print("It's warm outside!")
elif temperature > 5:
    print("It's cold outside!")
else:
    print("It's freezing outside!")

In this example, the message “It’s hot outside!” is printed because the condition temperature > 25 is true.

Nested if Statements

You can also nest if statements within other if, elif, or else statements to create more complex conditions.

Example:

age = 20
has_voter_id = True

if age >= 18:
    if has_voter_id:
        print("You can vote.")
    else:
        print("You need a voter ID to vote.")
else:
    print("You are not eligible to vote.")

In this example, the message “You can vote.” is printed because both conditions age >= 18 and has_voter_id are true.

Summary

• if: Executes a block of code if its condition is true.
• elif: Checks another condition if the previous conditions were false.
• else: Executes a block of code if all previous conditions were false.
• Nested if: Allows for more complex decision-making by nesting one if statement inside another.

These conditional statements allow you to control the flow of your program and make decisions based on different conditions.