How to call function iside a module dynamically?

Question

How to call a function inside a (code of a) module dynamically?

For example:

class Class1(object):
 pass
class Class2(object):
 pass
# here I want to either instantiate object dynamically or dynamically pass 
# a Class1 or Class2 object to some other method/class inside this module code

• Joel Cornett: You're going to have to be a bit more specific. Some more coded examples, perhaps?
• Philipp: What have you tried so far? In Python you can pass classes around like any other object.
• Wug: Python is weakly typed. There is nothing to restrict you from just passing an object of either type to any function

Answer 1

You mean something like this?

>>> class Class1(object):
... pass
... 
>>> class Class2(object):
... pass
... 
>>> def foo(cls):
... print cls
... 
>>> import random
>>> classes = {'Class1': Class1, 'Class2': Class2}
>>> dynamic_class = classes['Class%d' % random.randint(1, 2)]
>>> foo(dynamic_class())
<__main__.Class1 object at 0x10b44ab50>

• mgilson: I think this example would be a little more constructive if you explicitly created the dictionary that is being returned by locals().
• mgilson: Agreed. (+1) for your efforts (and nice example)

Answer 2

I'm assuming that you mean you want to access the classes by name.

If the class you want is in the same module, try globals()[classname]() to instantiate the class. If it's in another module, try vars(module)[classname]() or getattr(module, classname)().

(classname is a string containing the name of the class; module is a reference to the module, not a string.)

• mgilson: I've never seen vars(module)[classname](). Is there a reason to prefer this over getattr? (Or is this another Tomato, tomato thing?)
• kindall: I kind of like vars(modules) because it's analogous with globals()—you get back a dictionary with either so the rest is the same. Otherwise, matter of taste, I guess.