switch-case alternative in Python

Python has so 'switch - case' support unlike most other common languages. Of course you can use If-else block to serve your purpose. But there is an elegant alternative to 'switch-case' in python, using dictionary. Go though the following code (you should try running it).

# this is the default function
def errorMessage():
    print "Incorrect input. Please enter a number between 0 and 3."

def fnc0():
    print "This is function 0"

def fnc1():
    print "This is function 1"

def fnc2():
    print "This is function 2"

def fnc3():
    print "This is function 3"


fncDict = {'0': fnc0, '1': fnc1, '2': fnc2, '3': fnc3}

num = raw_input("Enter a number between 0 and 3")
# if num is found as a key in the dictionary fncDict, then corresponding function is called
# else the function errorMessage is called
fncDict.get(num, errorMessage)()


Hope you will find it interesting!

Comments

Unknown said…
Or you can make it even without dict:

num = raw_input("Enter a number between 0 and 3")

getattr(sys.modules[__name__], "fnc%s" % num, errorMessage)()

something like this ;)
April 3, 2010 at 4:13 PM
Paul Wand said…
This comment has been removed by the author.
April 21, 2010 at 4:24 AM
Paul Wand said…
You know, its probably better to avoid the use of the dict/switch statement and implement this with the use of inheritance/duck typing
April 21, 2010 at 4:34 AM
Taoelism said…
Thanks! Looks pretty neat. Ofcourse it won't be a really good replacement for case/switch.
June 19, 2010 at 4:42 PM
Anonymous said…
@Rapolas has the right idea for avoiding the redundancy of the dictionary, but doing a getattr() on the current module is unusual... just use globals(). Better yet, those functions should be methods on an object, in which case you'd be using getattr(self, 'fnc%s' % num). This is a widely used convention, often referred to using the term "dispatching".
September 12, 2010 at 6:02 AM
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