Python中Swithch Case语法实现

转载自：http://blog.csdn.net/suiyunonghen/article/details/3734135

其他语言中，switch语句大概是这样的

switch (var)
{
case value1: do_some_stuff1();
case value2: do_some_stuff2();
…
case valueN: do_some_stuffN();
default: do_default_stuff();
}


而python本身没有switch语句，解决方法有以下3种:
A.使用dictionary
values = {
value1: do_some_stuff1,
value2: do_some_stuff2,
…
valueN: do_some_stuffN,
}
values.get(var, do_default_stuff)()
[b]B.使用lambda
[/b][code]result = {
'a': lambda x: x * 5,
'b': lambda x: x + 7,
'c': lambda x: x - 2
}[value](x)

[b]C.Brian Beck提供了一个类 switch 来实现其他语言中switch的功能
[/b]
# 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 = value
self.fall = False

def __iter__(self):
“”“Return the match method once, then stop”“”
<
4000
/span>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

# 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



[/code]