python 装饰器不返回函数值

Question

我从装饰器开始，所以我尝试了一个基本示例调试装饰器，它打印函数名称、输入参数和输出值。下面是我的调试装饰器。

def debug(func):
    @functools.wraps(func)
    def wrapper_debug(*args, **kwargs):
        args_repr = [repr(a) for a in args]                     
        kwargs_repr = [f"{k}={v!r}" for k, v in kwargs.items()]  
        signature = ", ".join(args_repr + kwargs_repr)           
        print(f"Calling {func.__name__}({signature})")
        value = func(*args, **kwargs)
        print(f"{func.__name__!r} returned {value!r}")           
        return value
    return wrapper_debug

获取每个数字的阶乘以及我想要的所有这些阶乘的最终总和。无法获得阶乘的总和。即调试装饰器不返回原始函数值。

from decorator import debug
import math

math.factorial = debug(math.factorial)

def approximate_e(terms=18):
    return sum(1 / math.factorial(n) for n in range(terms))

approximate_e(5)

这是我在运行代码

时得到的输出

Calling factorial(0)
'factorial' returned 1
Calling factorial(1)
'factorial' returned 1
Calling factorial(2)
'factorial' returned 2
Calling factorial(3)
'factorial' returned 6
Calling factorial(4)
'factorial' returned 24

预期输出：

Calling factorial(0)
'factorial' returned 1
Calling factorial(1)
'factorial' returned 1
Calling factorial(2)
'factorial' returned 2
Calling factorial(3)
'factorial' returned 6
Calling factorial(4)
'factorial' returned 24
2.708333333333333

Answer 1

它做 return这个值，但是你不在调用后打印它...

这样做：

print(approximate_e(5))

python 装饰器不返回函数值

python decorator not returning function value

python

python-3.x

python-decorators