if…else Statement

What Will You Learn
In this lesson, you'll explore how Python uses if, else, and elif statements to execute code based on specific conditions. You'll learn the correct syntax, nesting strategies, and real-world use cases that require conditional branching. This foundation is crucial for building responsive, intelligent Python programs that adapt to different inputs and states.

Control flow statements like if, else, and elif are essential tools in any programming language, especially in Python. They allow your program to make decisions and execute certain blocks of code based on conditions. Without control flow, your script would execute sequentially from top to bottom, regardless of context or input. That would make it impossible to build dynamic, responsive, or interactive applications.

In Python, the if…else structure is one of the first decision-making tools you'll learn. It checks whether a condition is true and runs specific code accordingly. As a beginner, you’ll rely heavily on these constructs to control what your program does in different scenarios. They’re used in loops, validations, calculations, and almost every kind of logic.

What Does an if/else Statement Look Like in Python?

The if…else statement in Python checks a condition and chooses between two different blocks of code. If the condition evaluates to True, the if block runs. If it's False, the else block runs instead. This is one of the clearest and most readable decision-making structures in any programming language.

Here's the example of if else python in one line:

result = "Even" if number % 2 == 0 else "Odd"

In this example, the variable result will be assigned the string "Even" if number is even, and "Odd" if it is not.

Here's the basic syntax:

    x = 10
    if x > 5:
        print("x is greater than 5")
    else:
        print("x is 5 or less")

In this example, if x is greater than 5, the program prints "x is greater than 5". If not, it prints "x is 5 or less".

In Python, indentation is crucial. The code inside the if and else blocks must be indented to indicate that it belongs to that block. This is different from many other languages that use curly braces or keywords to define blocks.

Let’s break down the elements:

This structure is easy to scale with more logic using elif (short for “else if”), which we’ll discuss next.

How to Do Else If in Python

In Python, the equivalent of “else if” from other languages is written as elif. It allows you to check multiple conditions in sequence. The interpreter evaluates each if or elif condition in order and runs the first block where the condition is True. If none of them are true, and there is an else, that block runs by default.

Example:

    score = 85
    if score >= 90:
        print("Grade: A")
    elif score >= 80:
        print("Grade: B")
    else:
        print("Grade: C or lower")

Using elif helps avoid deeply nested if statements and keeps your logic readable and efficient.

What Is the Difference Between if and if else Statement in Python?

An if statement in Python checks a single condition and executes a block of code only if that condition is true. If the condition is false, nothing happens — the interpreter skips over the if block entirely. In contrast, an if…else structure allows you to handle both outcomes — when the condition is true and when it's false.

For example:

    # if only
    if x > 0:
        print("Positive number")

    # if...else
    if x > 0:
        print("Positive")
    else:
        print("Zero or negative")

The if…else form is more complete and ensures your program responds in all scenarios, not just when the condition is true.

Why Do We Use If/Else Statements in Python?

The if/else statement is one of the most important tools in programming because it allows your code to make decisions. In real-world programs, actions often depend on conditions — such as user input, data validation, or program state. Without control flow, a program would always behave the same way, regardless of the situation. That’s why conditional logic is essential for writing flexible and intelligent code.

Python’s if, elif, and else keywords give you full control over execution depending on multiple logical cases. It helps your program respond correctly, whether it's a login check, form input validation, or choosing between calculation branches. These structures also make your code cleaner and easier to understand.

Key reasons to use if/else in Python:

• User input validation. Check if the user entered correct data before continuing the program.
• Branching logic. Choose between multiple paths of execution depending on specific conditions.
• Error prevention. Avoid performing invalid operations (e.g., dividing by zero).
• Controlling program flow. Stop or redirect actions when certain criteria are not met.
• Dynamic behavior. Make the program react to different values or system states.
• Simple decision-making. Quickly evaluate whether a condition is met and take appropriate action.
• Combining with loops. Control execution within while or for loops based on dynamic logic.
• Fallback defaults. Provide a default behavior with else if none of the conditions are satisfied.

Common Beginner Mistakes

1. Missing Indentation After if or else Block

The mistake: Beginners often forget to indent the code that follows an if, else, or elif statement. Since indentation is syntactically required in Python, this leads to an IndentationError.

Incorrect:

    if x > 0:
    print("Positive number")

Correct:

    if x > 0:
        print("Positive number")

Solution: Always indent the block under if, else, or elif. The Python standard is 4 spaces.

2. Using elseif Instead of elif

The mistake: Developers with experience in other languages (like JavaScript or PHP) may use elseif, which is not valid in Python. This causes a SyntaxError.

Incorrect:

    if x > 0:
        print("Positive")
    elseif x == 0:
        print("Zero")

Correct:

    if x > 0:
        print("Positive")
    elif x == 0:
        print("Zero")

Solution: In Python, the correct keyword is elif — short for "else if."

3. Confusing = with ==

The mistake: New programmers sometimes confuse the assignment operator = with the equality operator ==. Using = in a condition raises a SyntaxError.

Incorrect:

    if x = 10:
        print("x is ten")

Correct:

    if x == 10:
        print("x is ten")

Solution: Use == when comparing values. Remember: = assigns, == compares.

4. Empty if or else Block

The mistake: Writing an if or else without any code inside it results in an IndentationError or logical confusion.

Incorrect:

    if x > 0:
    elif x == 0:
        print("Zero")

Correct:

    if x > 0:
        pass
    elif x == 0:
        print("Zero")

Solution: Use the pass keyword if you want a placeholder without actual logic yet.

5. Comparing Strings with Numbers Without Type Conversion

The mistake: Comparing a string input with a number without converting its type always returns False or causes a TypeError.

Incorrect:

    x = input("Enter a number: ")
    if x > 5:
        print("Greater than 5")

Correct:

    x = input("Enter a number: ")
    if int(x) > 5:
        print("Greater than 5")

Solution: Always convert strings to integers (int()) or floats (float()) before numerical comparisons.

6. Overusing Nested if Statements

The mistake: Beginners often create deeply nested if...else blocks, which makes the code hard to read and maintain.

Incorrect:

    if x > 0:
        if x < 10:
            if x % 2 == 0:
                print("Even and between 0 and 10")

Better:

    if 0 < x < 10 and x % 2 == 0:
        print("Even and between 0 and 10")

Solution: Combine conditions using logical operators (and, or) to reduce unnecessary nesting and improve clarity.

FAQ on if…else Statement in Python

    age = 20
    if age >= 18:
        print("You are an adult.")
    else:
        print("You are a minor.")

    score = 75
    if score >= 90:
        print("Grade A")
    elif score >= 70:
        print("Grade B")
    else:
        print("Grade C")

    def check_login(user):
    if user == "admin":
        print("Access granted")
        return
    else:
        print("Access denied")
        return

    temperature = 35
    if temperature > 30:
        print("It's hot today.")

    day = "Wednesday"
    if day == "Monday":
        print("Start of the week")
    elif day == "Wednesday":
        print("Midweek")
    elif day == "Friday":
        print("Almost weekend")
    else:
        print("Normal day")

    x = 3
    if x > 5:
        print("Greater than 5")
    elif x == 5:
        print("Equal to 5")