Decorator won't work: 'NoneType' object is not callable

Question

import numpy as np

def multi_print(n):
    def decorator(func):
        def wrapper(*args, **kwargs):
            for z in np.arange(n):
                print(func(*args))

@multi_print(2)   
def if_num(x):
    if x == 1:
        return 'abc'
    else:
        return 'def'

if_num(3)

I am trying to just play around with how decorators interact with functions. When I run this block of code, I get a 'NoneType' object is not callable error. Wasn't sure why. I would expect the above code to print "def" two times.

Answer 1

Your decorator and wrapper don't return anything. A decorator with arguments should return a decorator, and the decorator should return the wrapped function. The fix:

import numpy as np

def multi_print(n):
    def decorator(func):
        def wrapper(*args, **kwargs):
            for z in np.arange(n):
                print(func(*args, **kwargs)) # should pass on kwargs, too
        return wrapper
    return decorator

@multi_print(2)   
def if_num(x):
    if x == 1:
        return 'abc'
    else:
        return 'def'

if_num(3)

Output:

def
def