Python装饰器跳过装饰函数的代码

Question

This code skips the code in the number function:

def some_decorator(x):
     def wrapper(x):
         return x+1
     return wrapper

@some_decorator
def number(x):
    x = x + 100
    return x

Output:

>>> number(3)
4

I am trying to make the output of number(3) to be 104, what is wrong with the code?

Answer 1

Decorators pass the function as an argument to the decorator. It's your job to call the function if you want it to execute:

def some_decorator(fn):
    def wrapper(x):
         return fn(x) + 1 # call the function and add 1 
    return wrapper

@some_decorator
def n(x):
    x = x + 100
    return x

n(3) # 104

As a side note, it's often useful to use functools.wraps to make the wrapped function behave as expected:

from functools import wraps

def some_decorator(fn):
    @wraps(fn)
    def wrapper(x):
         return fn(x) + 1
    return wrapper

@some_decorator
def n(x):
    x = x + 100
    return x

print(n.__name__) # now prints `n` instead of `wrapper`