How to strip decorators from a function in Python

Question

Let's say I have the following:

def with_connection(f):     def decorated(*args, **kwargs):         f(get_connection(...), *args, **kwargs)     return decorated  @with_connection def spam(connection):     # Do something 

I want to test the spam function without going through the hassle of setting up a connection (or whatever the decorator is doing).

Given spam, how do I strip the decorator from it and get the underlying "undecorated" function?

Answer 1

There's been a bit of an update for this question. If you're using Python 3, you can use __wrapped__ property for decorators from stdlib.

Here's an example from Python Cookbook, 3rd edition, section 9.3 Unwrapping decorators

>>> @somedecorator >>> def add(x, y): ...     return x + y ... >>> orig_add = add.__wrapped__ >>> orig_add(3, 4) 7 >>> 

If you are trying to unwrap a function from custom decorator, the decorator function needs to use wraps function from functools See discussion in Python Cookbook, 3rd edition, section 9.2 Preserving function metadata when writing decorators

>>> from functools import wraps >>> def somedecorator(func): ...    @wraps(func) ...    def wrapper(*args, **kwargs): ...       # decorator implementation here ...       # ...... ...       return func(*args, **kwargs) ... ...    return wrapper