在 Python3 中创建装饰器时出现问题

Question

谁能告诉我我犯了什么错误。

装饰器

import time

def f1(f):

    a = time.time()
    f()
    b = time.time()
    c = b-a
    print("time required is", c)
@f1

def f3(f2):
    
    n = []
    for i in range(1000):
        n.append(i)
    print(sum(n), "for F3")
    f2()

@f3

def f4():

    n = []
    for i in range(1000):
       n.append(i)
    print(sum(n), "for F4")

f4

o/p:

回溯（最近调用最后）：

File "C:/test.py", line 13, in <module>

@f1

File "C:/test.py", line 7, in f1

f()

TypeError: f3() missing 1 required positional argument: 'f2'

Process finished with exit code 1

希望实现这样的目标：

def decorator_with_args(decorator_to_enhance):

def decorator_maker(*args, **kwargs):

    def decorator_wrapper(func):

        return decorator_to_enhance(func, *args, **kwargs)

    return decorator_wrapper

return decorator_maker

@decorator_with_args

def decorated_decorator(func, *args, **kwargs):

def wrapper(function_arg1, function_arg2):

    print("Decorated with {0} {1}".format(args, kwargs))

    return func(function_arg1, function_arg2)

return wrapper

@decorated_decorator(42, 404, 1024)

def decorated_function(function_arg1, function_arg2):

print("Hello {0} {1}".format(function_arg1, function_arg2))

decorated_function("宇宙与","一切")

Answer 1

虽然您可以在另一个没有 return 任何可调用对象的单个函数中包装和运行，但请记住，包装后的函数不再可调用。因此，当计时对象不需要原始对象的可重用性时，您当前的代码有效：

import time
def timeit(f):
  c = time.time()
  _ = f()
  c2 = time.time()
  print(f"'{f.__name__}' took {c2-c}s")

@timeit
def f2():
  return sum(range(1000))

输出（不调用f2）：

'f2' took 8.988380432128906e-05s

但是，如果尝试调用 f2:

_ = f2()

Traceback (most recent call last): File "", line 1, in TypeError: 'NoneType' object is not callable

为防止上述错误，在装饰函数中创建一个包装函数：

def timeit(f):
 def wrapper(*args, **kwargs):
    c = time.time()
    _result = f(*args, **kwargs)
    c2 = time.time()
    print(f"'{f.__name__}' took {c2-c}s")
    return _result
 return wrapper

@timeit
def f2():
  return sum(range(1000))

f2直到被调用才会被计时，触发wrapper:

print(f2())

输出：

'f2' took 3.981590270996094e-05s
499500

在 Python3 中创建装饰器时出现问题

Issue creating decorator in Python3

python

python-3.x

python-decorators

装饰器