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How to Exit from if Statements in Python

This guide explains how to control the flow of execution within and around if statements in Python. We'll cover exiting if blocks, exiting functions containing if statements, and exiting loops that contain if statements. We'll focus on using return, break, raise (with try/except), if/elif/else chains, and briefly touch on sys.exit() with a strong caution.

Exiting an if Block (and Function) with return​

The return statement immediately exits the current function, and therefore also exits any if statement within that function. This is the standard way to exit an if block and the containing function simultaneously.

def my_function(num):
    if num > 0:
        print('num > 0')
        return  # Exits the if AND the function
    if num < 0:
        print('num < 0')
        return  # Exits the if AND the function

    print('num = 0')
    return

my_function(100)    # Output: num > 0
my_function(-30)    # Output: num < 0
my_function(0)      # Output: num = 0
  • return without a value implicitly returns None.
  • Any code after a return statement within that function's scope will not be executed.
  • You can also return specific values based on condition.
def my_function(num):
    if num > 0:
        print('num > 0')
        return 'A'
    if num < 0:
        print('num < 0')
        return 'B'

    print('num = 0')
    return 'C'


result = my_function(100)
print(result)  # Output: A
result = my_function(-30)
print(result)  # Output: B
result = my_function(0)
print(result)  # Output: C

Exiting an if Block and Loop with break​

The break statement exits the innermost enclosing loop (for or while), also exiting any if statement within that loop.

for i in range(1, 7):
    print(i)        # Prints 1, then 2, then 3
    if i == 3:
        print(i)    # Prints 3
        break       # Exits the if AND the for loop
    if i == 6:      # This will never run in this case
        print(i)
        break

Output

1
2
3
3

You can also use it with a while loop.

num = 6
while num > 0:
    if num % 2 == 0:
        num = num - 10
        break           # Exit the while loop and the if statement
    if num % 3 == 0:    # Never runs as previous condition is always met first
        num = num - 20
        break
    break               # Always executes if the loop starts

print(num)  # Output: -4

Exiting with raise and try/except​

The raise keyword throws an exception. This immediately stops execution of the current block of code (including any if statement) and propagates the exception up the call stack. You must use a try/except block to handle raised exceptions, or your program will terminate.

num = 6

try:
    if num % 2 == 0:
        print('Number is divisible by 2')
        raise ValueError('some error')  # Exit if AND raise exception
        print('This will not run')
except ValueError:
    print('Except block runs') # Output: Except block runs
  • In this case an exception is raised, so the except block is executed.
  • If you don't know the type of exceptions that may be raised, use the generic Exception class.
def example():
    a = 123
    raise ValueError('invalid value')

try:
    example()
except Exception as e:
    print('A ValueError occurred...', e) # Output: A ValueError occurred... invalid value

Using if/elif/else for Multiple Conditions​

Often, you don't want to exit, but rather handle different conditions sequentially. Use if/elif/else for this:

num = 9
if num > 10:
    print('num > 10')
elif num > 9:
    print('num > 9')  # This won't run, because 9 is not > 10
elif num > 8:
    print('num > 8') # Output: num > 8 (this runs)
else:
    print('else block runs')
  • The if, elif, and else blocks provide a structured way to handle different cases without prematurely exiting.

Exiting the Program with sys.exit() (Use with Caution)​

The sys.exit() function terminates the entire Python script. This should generally be used sparingly, as it's a very abrupt way to end program execution. It should only be used at the end of the script, and other exit methods described above are recommended.

import sys

num = 9
if num == 9:
    print('num > 10')
    sys.exit()  # Exits the ENTIRE script
    print('This never runs')
warning

Avoid overusing sys.exit(). It's generally better to structure your code with return, break, and exception handling to control program flow. sys.exit() should be reserved for situations where the program can not continue, such as unrecoverable errors or reaching a deliberate termination point.

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