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A Python implementation of a switch-case statement helper that mimics C-style switch behavior with fall-through support.

Purpose

This class provides a Pythonic way to implement switch-case logic, commonly used for menu selection and multi-branch conditionals. It supports fall-through behavior (like C's switch statement) where once a case matches, all subsequent cases execute until explicitly stopped. The class is designed to be used with Python's for-in loop syntax to create readable switch-case structures.

Source Code

class switch(object):
    # Helper function to build long "case" choice functions - used in menu selection
    def __init__(self, value):
        self.value = value
        self.fall = False

    def __iter__(self):
        """Return the match method once, then stop"""
        yield self.match
        raise StopIteration
    
    def match(self, *args):
        """Indicate whether or not to enter a case suite"""
        if self.fall or not args:
            return True
        elif self.value in args: # changed for v1.5, see below
            self.fall = True
            return True
        else:
            return False

Parameters

Parameter Details

value: The value to be matched against in case statements. This is the expression being switched on, similar to the value in 'switch(value)' in C-style languages. Can be any comparable Python object (string, int, etc.).

Return Value

Instantiation returns a switch object that can be iterated over. The match() method returns a boolean: True if the case should execute (either because it matches, fall-through is active, or no arguments provided for default case), False otherwise.

Class Interface

Methods

Attributes

Usage Example

# Basic switch-case usage
value = 2
for case in switch(value):
    if case(1):
        print('Case 1')
        break
    if case(2, 3):
        print('Case 2 or 3')
        break
    if case(4):
        print('Case 4')
        break
    if case():
        print('Default case')
        break

# Menu selection example
user_choice = 'save'
for case in switch(user_choice):
    if case('save', 's'):
        print('Saving file...')
        break
    if case('load', 'l'):
        print('Loading file...')
        break
    if case('quit', 'q'):
        print('Quitting...')
        break
    if case():
        print('Invalid option')

# Fall-through example (without break)
value = 2
for case in switch(value):
    if case(1):
        print('One')
    if case(2):
        print('Two')
    if case(3):
        print('Three')
    if case():
        print('Done')

Best Practices

• Always use the switch class within a for-in loop: 'for case in switch(value):'
• Use break statements after each case to prevent fall-through behavior (unless fall-through is desired)
• Call case() with no arguments to create a default case that always matches
• The match() method can accept multiple values: case(1, 2, 3) matches if value is 1, 2, or 3
• Once a case matches, self.fall is set to True, causing all subsequent cases to execute until the loop breaks
• The iterator yields the match method only once, so the for loop body executes exactly once
• This pattern is most useful for menu systems and multi-way branching where readability is important
• Not thread-safe due to mutable state (self.fall); create separate instances for concurrent use

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