Python function pointer

Question

I have a function name stored in a variable like this   myvar    mypackage mymodule myfunction    and I now want to call myfunction like this  myvar parameter1  parameter2    What s the easiest way to achieve this

User · Answer

I ran into a similar problem while creating a library to handle authentication. I want the app owner using my library to be able to register a callback with the library for checking authorization against LDAP groups the authenticated person is in. The configuration is getting passed in as a config.py file that gets imported and contains a dict with all the config parameters.

I got this to work:

>>> class MyClass(object):
...     def target_func(self):
...         print "made it!"
...    
...     def __init__(self,config):
...         self.config = config
...         self.config['funcname'] = getattr(self,self.config['funcname'])
...         self.config['funcname']()
... 
>>> instance = MyClass({'funcname':'target_func'})
made it!

Is there a pythonic-er way to do this?

User · Answer

funcdict        mypackage mymodule myfunction   mypackage mymodule myfunction              funcdict myvar  parameter1  parameter2

User · Answer

Easiest  eval myvar  parameter1  parameter2    You don t have a function  pointer    You have a function  name    While this works well  you will have a large number of folks telling you it s  insecure  or a  security risk

User · Answer

It s much nicer to be able to just store the function itself  since they re first-class objects in python   import mypackage  myfunc   mypackage mymodule myfunction myfunc parameter1  parameter2    But  if you have to import the package dynamically  then you can achieve this through   mypackage     import    mypackage   mymodule   getattr mypackage   mymodule   myfunction   getattr mymodule   myfunction    myfunction parameter1  parameter2    Bear in mind however  that all of that work applies to whatever scope you re currently in  If you don t persist them somehow  you can t count on them staying around if you leave the local scope

User · Answer

modname  funcname   myvar rsplit      1  getattr sys modules modname   funcname  parameter1  parameter2

User · Answer

def f a b       return a b  xx    f  print eval   s  s  s    xx 2 3     OUTPUT   5

User · Answer

eval compile myvar   lt str gt    eval    myargs   compile      eval   allows only a single statement  so that there can t be arbitrary commands after a call  or there will be a SyntaxError  Then a tiny bit of validation can at least constrain the expression to something in your power  like testing for  mypackage  to start

User · Answer

Why not store the function itself  myvar   mypackage mymodule myfunction is much cleaner

[python] Python function pointer

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