在Python开发过程中，很多时候都需要使用到switch的结构形式，而大多在遇到这种情况的时候，开发人员都是使用if...else...结构来代替，但是过多的重复判断，会导致程序的可读性变差。

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class switch(object):
    """
    This class provides the functionality we want. You only need to look at
    this if you want to know how this works. It only needs to be defined
    once, no need to muck around with its internals.
    """
    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:
            self.fall = True
            return True
        else:
            return False


# The following example is pretty much the exact use-case of a dictionary,
# but is included for its simplicity. Note that you can include statements
# in each suite.
"""
v = 'ten'
for case in switch(v):
    if case('one'):
        print(1)
        break
    if case('two'):
        print(2)
        break
    if case('ten'):
        print(10)
        break
    if case('eleven'):
        print(11)
        break
    if case(): # default, could also just omit condition or 'if True'
        print("something else!")
        # No need to break here, it'll stop anyway
"""
# break is used here to look as much like the real thing as possible, but
# elif is generally just as good and more concise.

# Empty suites are considered syntax errors, so intentional fall-throughs
# should contain 'pass'
"""
c = 'z'
for case in switch(c):
    if case('a'): pass # only necessary if the rest of the suite is empty
    if case('b'): pass
    # ...
    if case('y'): pass
    if case('z'):
        print("c is lowercase!")
        break
    if case('A'): pass
    # ...
    if case('Z'):
        print("c is uppercase!")
        break
    if case(): # default
        print("I dunno what c was!")
"""
# As suggested by Pierre Quentel, you can even expand upon the
# functionality of the classic 'case' statement by matching multiple
# cases in a single shot. This greatly benefits operations such as the
# uppercase/lowercase example above:
"""
import string
c = 'A'
for case in switch(c):
    if case(*string.lowercase): # note the * for unpacking as arguments
        print "c is lowercase!"
        break
    if case(*string.uppercase):
        print("c is uppercase!")
        break
    if case('!', '?', '.'): # normal argument passing style also applies
        print("c is a sentence terminator!")
        break
    if case(): # default
        print("I dunno what c was!")
"""
# Since Pierre's suggestion is backward-compatible with the original recipe,
# I have made the necessary modification to allow for the above usage.