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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, particularly useful for menu selection systems. It allows matching a value against multiple cases and supports fall-through behavior (continuing to execute subsequent cases after a match). 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 a C switch statement. Can be any comparable Python object (string, integer, etc.).

Return Value

Instantiation returns a switch object that can be iterated over. The match() method returns a boolean: True if the case should be entered (either due to matching, fall-through, or default case), False otherwise.

Class Interface

Methods

Attributes

Usage Example

# Basic usage for menu selection
for case in switch(user_choice):
    if case('option1'):
        print('Handling option 1')
        break
    if case('option2', 'option3'):
        print('Handling option 2 or 3')
        break
    if case():
        print('Default case')
        break

# Example with fall-through (no break)
choice = 2
for case in switch(choice):
    if case(1):
        print('Case 1')
        # No break - will fall through
    if case(2):
        print('Case 2')
        # No break - will fall through
    if case(3):
        print('Case 3')
        break

Best Practices

• Always use the class within a for-in loop: 'for case in switch(value):'
• Call the match() method using 'if case(...)' syntax within the loop
• Use 'break' after each case block to prevent fall-through unless fall-through is desired
• Call case() with no arguments to create a default case that always matches
• Multiple values can be passed to a single case() call to match any of them
• The iterator yields the match method only once, so the loop body executes exactly once
• Once a case matches, self.fall is set to True, causing all subsequent cases to match (fall-through behavior)
• This class is stateful - each instantiation maintains its own match state

Tags

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