本文主要是介绍Python中 Switch/Case 实现，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
学习Python过程中，发现没有switch-case,过去写C习惯用Switch/Case语句，官方文档说通过if-elif实现。所以不妨自己来实现Switch/Case功能。
方法一
通过字典实现
def foo(var):return {'a': 1，'b': 2,'c': 3,}.get(var,'error') #'error'为默认返回值，可自设置方法二
通过匿名函数实现
def foo(var,x):return {'a': lambda x: x+1,'b': lambda x: x+2,'c': lambda x: x+3, }[var](x)方法三
通过定义类实现
参考Brian Beck通过类来实现Swich-case
# 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.
class switch(object):def __init__(self, value):self.value = valueself.fall = Falsedef __iter__(self):"""Return the match method once, then stop"""yield self.matchraise StopIterationdef match(self, *args):"""Indicate whether or not to enter a case suite"""if self.fall or not args:return Trueelif self.value in args: # changed for v1.5, see belowself.fall = Truereturn Trueelse: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 1breakif case('two'):print 2breakif case('ten'):print 10breakif case('eleven'):print 11breakif 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 emptyif case('b'): pass# ...if case('y'): passif case('z'):print "c is lowercase!"breakif case('A'): pass# ...if case('Z'):print "c is uppercase!"breakif case(): # defaultprint "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 argumentsprint "c is lowercase!"breakif case(*string.uppercase):print "c is uppercase!"breakif case('!', '?', '.'): # normal argument passing style also appliesprint "c is a sentence terminator!"breakif case(): # defaultprint "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.查看Python官方:PEP 3103-A Switch/Case Statement
发现其实实现Switch Case需要被判断的变量是可哈希的和可比较的，这与Python倡导的灵活性有冲突。在实现上，优化不好做，可能到最后最差的情况汇编出来跟If Else组是一样的。所以Python没有支持。
在业务上Switch/Case和If-elif实现优化上究竟最差是如何？有体会的童鞋欢迎评论分享探讨哈！O(∩_∩)O
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