Conditional Statements

In Python, conditional statements are used to make decisions in the code based on certain conditions. They allow us to execute different blocks of code depending on whether a specific condition evaluates to True or False.

Types of Conditional Statements in Python

Python has following conditional statements:

if-else statement

If the condition in the if statement evaluates to true, the code inside the if block will be executed; otherwise, the code within the else block will be executed.

Syntax:

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

Example:

num = int(input("Enter a number: "))
if num < 0:
  print("Number is negative.")
else:
  print("Number is positive.")

elif statement

The elif statement (short for "else if") is used when there are multiple conditions to evaluate. It is placed between if and else.

Syntax:

if condition1:
    # Code to execute if condition1 is True
elif condition2:
    # Code to execute if condition2 is True
else:
    # Code to execute if all above conditions are False

Example:

num = int(input("Enter a number: "))
if num < 0:
    print("Number is negative.")
elif num == 0:
    print("Number is zero.")
else:
    print("Number is positive.")

Nested if statements

if statements can be nested within other if, elif, or else blocks to evaluate additional conditions.

Syntax:

if condition1:
    # Code to execute if condition1 is True
    if condition2:
        # Code to execute if condition2 is True
    elif condition3:
        # Code to execute if condition3 is True
    else:
        # Code to execute if all inner conditions are False
else:
    # Code to execute if condition1 is False

Example:

num = int(input("Enter a number: "))
if num < 0:
    print("Number is negative.")
elif num > 0:
    if num <= 50:
        print("Number is between 1 and 50.")
    elif num > 50 and num <= 70:
        print("Number is between 51 and 70.")
    else:
        print("Number is greater than 70.")
else:
    print("Number is zero.")

Key Points About Conditional Statements

1. Indentation Matters:
   • Python uses indentation (spaces or tabs) to show which code belongs to a condition.
   • Make sure all lines in a block have the same indentation.
2. Only One else:
   • You can use many if and elif statements, but only one else is allowed.
3. Comparison and Logical Operators:
   • Conditions use operators like:
     • == (equal), != (not equal), < (less than), > (greater than).
     • and, or, not to combine conditions.
4. Order of Checks:
   • Python checks conditions one by one. If a condition is true, the following conditions are skipped.