if (判斷式1):
程式區塊1
elif(判斷式2):
程式區塊2
else:
程式區塊3
※如果「判斷式1」成立、執行「程式區塊1」，否則、如果，「判斷式2」成立、執行「程式區塊2」，否則執行「程式區塊3」。
冒號之後按Enter則下一行縮排，縮排是Python用來決定執行那些程式區塊的依據。
Python語言少了switch這個指令，最常用的方式是使用「字典」來對應。
英文參考網址：https://code.activestate.com/recipes/410692/
def foo(var):
return {
'a': 1，
'b': 2,
'c': 3,
}.get(var,'error')#如果沒找到就回傳error
另一個例子：
def f(x):
return {
'a': 1,
'b': 2,
}.get(x, 9) # 9 will be returned default if x is not found
def foo(var,x):
return {
'a': lambda x: x 1,
'b': lambda x: x 2,
'c': lambda x: x 3,
}[var](x)
節錄自：https://code.activestate.com/recipes/410692/
# 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
# 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.