Section 1.1: The If Statement

The if statement is your primary mechanism for introducing conditions in your code. It allows a block of code to run only when a specified condition is satisfied.

Example of a Basic If Statement:

temperature = 25

if temperature > 30:

print("It's a hot day!")

In this case, the code within the if block will execute solely if the temperature exceeds 30.

Section 1.2: Implementing If-Else Statements

An if-else statement provides an alternative pathway for your code when the initial condition isn't met.

Example of an If-Else Statement:

age = 18

if age >= 18:

print("You are eligible to vote!")

else:

print("You are not eligible to vote yet.")

Here, if the age is 18 or older, the first print statement runs; otherwise, the second statement within the else block executes.

Section 1.3: Handling Multiple Conditions with Elif

The elif statement is useful for evaluating multiple conditions in a sequence, effectively meaning "else if."

Example of an Elif Statement:

grade = 85

if grade >= 90:

print("A Grade")

elif 80 <= grade < 90:

print("B Grade")

elif 70 <= grade < 80:

print("C Grade")

else:

print("Below C Grade")

This example assesses the grade and displays the corresponding message based on the conditions set forth in the if, elif, and else statements.

Section 1.4: Using Logical Operators to Combine Conditions

Logical operators like and, or, and not allow for the combination of multiple conditions in your control flow statements.

Example of Logical Operators:

is_sunny = True

temperature = 28

if is_sunny and temperature > 25:

print("Perfect weather for a picnic!")

elif is_sunny or temperature > 25:

print("It's either sunny or warm.")

else:

print("Not ideal weather.")

In this instance, the code checks if both conditions are true for a picnic or if at least one is true. The else block addresses the situation when neither condition holds.

Section 1.5: Nested Control Flow for Complex Scenarios

You can nest control flow statements within one another to handle more intricate situations.

Example of Nested Control Flow:

is_weekend = True

if is_sunny:

if is_weekend:

print("Perfect weekend for outdoor activities!")

else:

print("Consider planning outdoor activities for the weekend.")

else:

print("Wait for a sunny day.")

This example evaluates if it’s sunny and, if so, further checks if it’s the weekend to provide tailored messages based on the nested conditions.

Section 2.1: User Input Validation

Control flow statements are frequently used for validating user inputs in real-world applications.

Example of User Input Validation:

user_age = int(input("Enter your age: "))

if user_age >= 18:

print("Welcome! You are eligible to access this content.")

else:

print("Sorry, this content is only available for users 18 years and older.")

This code prompts the user to input their age, converts it to an integer, and checks whether they qualify to access specific content based on age.

Best Practices for Control Flow Statements

• Use Clear Conditions: Formulate your conditions to be understandable and meaningful, enhancing code readability.
• Attention to Indentation: Python relies on indentation to define code blocks. Maintain consistent indentation for proper execution.
• Organize Conditions: Arrange your conditions from the most specific to the least specific. The first true condition will be executed.
• Simplify Complex Conditions: Break down overly complex conditions into simpler ones using elif statements for improved comprehension.