Executing a function by variable name in Python

Question

What I need to do is loop over a large number of different files and (try to) fetch metadata from the files.

I can make a large if...elif... and test for every extension, but I think it would be much easier to store the extension in a variable, check if a function with that name exists, and execute it.

This is my current solution, taken from another stackoverflow thread:

try:
    getattr(modulename, funcname)(arg)
except AttributeError:
    print 'function not found "%s" (%s)' % (funcname, arg)

There is a problem with this: If the underlying function raises an AttributeError, this is registered as a "function not found" error. I can add try...except blocks to all functions, but that would not be particularly pretty either ...

What I'm looking for is more something like:

if function_exists(fun):
  execute_function(fun, arg)

Is there a straightforward way of doing this?

Thanks :-)

Answer 1

You can do :

func = getattr(modulename, funcname, None):
if func:
    func(arg)

Or maybe better:

try:
    func = getattr(modulename, funcname)
except AttributeError:
    print 'function not found "%s" (%s)' % (funcname, arg)
else:
    func(arg)