Python IF/ELSE & Nested IF-ELSE Control Flow Statements

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In this article, we will explore the Python if-else control flow statements, which are quite similar to those in other programming languages like C, C++, and Java.

By default, a program executes its instructions sequentially. However, to achieve the desired output, you often need to control the flow of execution. This is where control flow statements come into play.

Control Flow IF-ELSE Statements:

  1. IF-ELSE
  2. Nested IF-ELSE

Python IF-ELSE

The if-else statement in Python is used to evaluate a condition and execute a block of statements based on whether the condition is true or false.

General Syntax:

				If (Condition):
    Statement(s)
Else:
    Statement(s)

 

Python Syntax:

Python syntax for if-else statements requires proper indentation, which is crucial for correct code execution. A single extra space can lead to errors, so be mindful of the indentation levels.

Example:

				if condition:
    # Statement(s) for true condition
else:
    # Statement(s) for false condition

Note: Remember that Python keywords such as if and else must be written in lowercase. Using uppercase will result in a syntax error, as Python is case-sensitive.

2. Nested IF-ELSE

While a simple if-else statement works for basic conditions, the nested if-else structure becomes valuable when dealing with multiple conditions, where each condition depends on the outcome of another. This approach allows you to handle complex logic by nesting if-else statements within one another, providing greater flexibility and control over your code.

Advantages of Nested IF-ELSE:

  • Flexibility: You can evaluate multiple conditions and execute different blocks of code based on a series of checks.
  • Efficiency: When a condition evaluates to true, subsequent conditions are skipped, which can reduce execution time.

Syntax:

				if condition1:
    # Statement(s) for condition1 being true
    if condition2:
        # Statement(s) for condition2 being true
    elif condition3:
        # Statement(s) for condition3 being true
    else:
        # Statement(s) for condition2 and condition3 being false
elif condition4:
    # Statement(s) for condition4 being true
else:
    # Statement(s) when none of the above conditions are true

Important Note: Ensure that if, elif, and else are written in lowercase.

Using uppercase or incorrect syntax like elseif instead of elif will result in a syntax error.

Python is very particular about syntax and case sensitivity, so adherence to the correct format is crucial.

Example:

				if temperature > 30:
    print("It's a hot day.")
    if humidity > 70:
        print("It's also quite humid.")
    elif humidity > 50:
        print("The humidity is moderate.")
    else:
        print("The air is relatively dry.")
elif temperature > 20:
    print("It's a pleasant day.")
else:
    print("It's a bit chilly.")

 

Summary

In this article, we explored Python’s if-else and nested if-else statements, which help control how your program runs based on different conditions.

The basic if-else statement lets you choose between two options depending on whether a condition is true or false. For more complex situations where conditions depend on one another, nested if-else statements provide a way to handle multiple checks.

Getting the syntax and indentation right is essential in Python, as mistakes can cause errors. By understanding and using these control flow tools effectively, you can write code that is clear, efficient, and able to handle complex logic.

Mastering these techniques will help you create programs that respond to various conditions and behave as expected.

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