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();
- }
A.使用dictionary
values = {
value1: do_some_stuff1,
value2: do_some_stuff2,
...
valueN: do_some_stuffN,
}
values.get(var, do_default_stuff)()
B.使用lambda
result = {
'a': lambda x: x * 5,
'b': lambda x: x + 7,
'c': lambda x: x - 2
}[value](x)C.Brian Beck提供了一个类 switch 来实现其他语言中switch的功能
# 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""" 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
