Using Variables for Class Names in Python?

python dynamic-typing
Sam McAfee picture Sam McAfee · Oct 21, 2008 · Viewed 44.9k times · Source

I want to know how to use variables for objects and function names in Python. In PHP, you can do this:

$className = "MyClass";

$newObject = new $className();

How do you do this sort of thing in Python? Or, am I totally not appreciating some fundamental difference with Python, and if so, what is it?

Answer

Jason Baker picture Jason Baker · Oct 21, 2008

Assuming that some_module has a class named "class_name":

import some_module
klass = getattr(some_module, "class_name")
some_object = klass()

I should note that you should be careful here: turning strings into code can be dangerous if the string came from the user, so you should keep security in mind in this situation. :)

One other method (assuming that we still are using "class_name"):

class_lookup = { 'class_name' : class_name }
some_object = class_lookup['class_name']()  #call the object once we've pulled it out of the dict

The latter method is probably the most secure way of doing this, so it's probably what you should use if at all possible.

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