Klaus Neuner wrote:
Hello,
I am writing a program that analyzes files of different formats. I
would like to use a function for each format. Obviously, functions can
be mapped to file formats. E.g. like this:
if file.endswith('xyz'):
xyz(file)
elif file.endswith('abc'):
abc(file)
...
Yet, I would prefer to do something of the following kind:
func = file[-3:]
apply_func(func, file)
As mentioned, a dictionary dispatch will do what you want, but you can
also use the self-registering technique outlined here:
http://effbot.org/zone/metaclass-plugins.htm [Fredrik Lundh]
(For Plugin, read Handler in this case.)
One idea might be to have Handler classes such as:
class TextHandler(HandlerType):
extensions = ['', 'txt', 'rst']
def run(self, *args, **kw):
.... do stuff
then the __init__ of HandlerType's metaclass:
def __init__(cls, name, bases, attrs):
for ext in attrs.get('extensions', []):
registry[ext] = cls
then use like:
registry['txt']().run()
If you don't need state, you could perhaps make 'run' a staticmethod and
store it rather than the class,
eg. registry[ext] = cls.run
and then just:
registry['txt']()
hth
G.F
------------------------------------------------------------------------
registry = {}
class HandlerType(object):
class __metaclass__(type):
def __init__(cls, name, bases, attrs):
for ext in attrs.get('extensions', []):
registry[ext] = cls
class TextHandler(HandlerType):
extensions = ['', 'txt']
print registry
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