Python If-Else Statements

The if-else statement is one of the most fundamental and frequently used concepts in programming. It is used to make decisions in your code. Based on the evaluation of a given condition, the program can take different actions. If the condition is True, the program will execute the block of code under the if statement, and if the condition is False, it will execute the block of code under the else statement.

What is an if-else Statement?

An if-else statement is a simple conditional structure that allows your program to execute one block of code when a condition is true and another block when it is false. It helps in decision-making by controlling the flow of execution.

The syntax of an if-else statement typically looks like this:

Syntax of if-else Statement

Syntax


if condition:
# Code block to execute if condition is True
else:
# Code block to execute if condition is False

Explanation:

In the above syntax, the condition is a boolean expression that evaluates to either True or False. Based on the evaluation of the condition, either the code inside the if block or the else block will be executed.

If the condition is true, the code within the if block runs. If the condition is false, the code inside the else block runs instead.

Example


x = 10
y = 20

if x == y:
print("x is equal to y")
else:
print("x is not equal to y")

Output

x is not equal to y

In this example, the condition x == y is evaluated. Since 10 == 20 is False, the program prints x is not equal to y.

What is the Difference Between if-else and elif?

In some cases, you may want to check multiple conditions. The elif (short for "else if") statement is used when you want to check more than two conditions. The if-elif-else structure is useful when you need to test several expressions for true or false.

Syntax of if-elif-else Statement

Syntax


if condition1:
# Code block to execute if condition1 is True
elif condition2:
# Code block to execute if condition2 is True
else:
# Code block to execute if none of the conditions are True

Explanation:

With if-elif-else, you can check multiple conditions. If the first condition is false, it moves on to the next condition, and so on. The else block at the end runs if all the conditions are false.

Example


# Example:
x = 10
y = 20

if x > y:
print("x is greater than y")
elif x < y:
print("x is less than y")
else:
print("x is equal to y")

Output

x is less than y

In this example, the first condition checks if x > y, which is false. So, the program moves on to check the next condition, x < y, which is true. Therefore, it prints x is less than y.

Nested if Statements

Sometimes, you may need to test conditions within another condition. This is known as a "nested if" statement. It allows you to add more layers of decision-making.

Syntax of Nested if Statements

Syntax


if condition1:
# Code block to execute if condition1 is True
if condition2:
    # Code block to execute if condition2 is True
else:
    # Code block to execute if condition2 is False
else:
# Code block to execute if condition1 is False

Example


# Example:
x = 10
y = 20

if x == 10:
if y == 20:
    print("x is 10 and y is 20")
else:
    print("x is 10 but y is not 20")
else:
print("x is not 10")

Output

x is 10 and y is 20

In this example, the first condition checks if x == 10, which is true. Then, it checks if y == 20, which is also true, so it prints x is 10 and y is 20.

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