2025-08-26

python中的一些注解解释

@wraps

functools is a standard Python module for higher-order functions (functions that act on or return other functions). wraps() is a decorator that is applied to the wrapper function of a decorator. It updates the wrapper function to look like wrapped function by copying attributes such as name, doc(the docstring), etc.

Syntax: @functools.wraps(wrapped, assigned = WRAPPER_ASSIGNMENTS, updated = WRAPPER_UPDATES)

Parameters: wrapped: The function name that is to be decorated by wrapper function. assigned : Tuple to specify which attributes of the original function are assigned directly to the matching attributes on the wrapper function. By default set to WRAPPER_ASSIGNMENTS (which assigns to the wrapper function’s module, name, qualname, annotations and doc, the documentation string) updated : Tuple to specify which attributes of the wrapper function are updated with the corresponding attributes from the original function. By default set to WRAPPER_UPDATES (which updates the wrapper function’s dict, i.e. the instance dictionary).

在缺失@wraps时，如下代码的输出是这样的

def a_decorator(func):
def wrapper(*args, **kwargs):
    """A wrapper function"""
    # Extend some capabilities of func
    func()
return wrapper

@a_decorator def first_function(): """This is docstring for first function""" print("first function") @a_decorator def second_function(a): """This is docstring for second function""" print("second function") print(first_function.name) print(first_function.doc) print(second_function.name) print(second_function.doc)

**wrapper  
 A wrapper function  
wrapper  
A wrapper function**

虽然上面的代码在逻辑上可以正常工作，但如果你正在编写一个 API 或库，并且有人想知道你的函数做什么，它的名称或只是简单地键入 help（yourFunction），请考虑这一点，它将始终显示包装函数的名称和文档字符串 。如果您对不同的函数使用相同的包装函数，这会更加混乱，因为它将为每个函数显示相同的详细信息。

理想情况下，它应该显示包装函数的名称和文档字符串，而不是包装函数。手动解决方案是在返回之前在包装函数中分配__name____doc__属性。

def a_decorator(func):
def wrapper(*args, **kwargs):
    """A wrapper function"""
    # Extend some capabilities of func
    func()
wrapper.__name__ = func.__name__
wrapper.__doc__ = func.__doc__
return wrapper

@a_decorator def first_function(): """This is docstring for first function""" print("first function") @a_decorator def second_function(a): """This is docstring for second function""" print("second function") print(first_function.name) print(first_function.doc) print(second_function.name) print(second_function.doc)

这样子拷贝过去可以解决一定问题，但是如果我们再次键入 help（yourFunction） 会怎样

First Function

Help on function first_function in module main: first_function(*args, **kwargs) This is docstring for first function

Second Function Help on function second_function in module main: second_function(*args, **kwargs) This is docstring for second function

如您所见，它仍然存在一个问题，即函数的签名，它显示了包装函数使用的签名（这里是通用签名）每个函数的签名。此外，如果您要实现许多装饰器，那么您必须为每个装饰器编写这些行。
因此，为了节省时间并提高可读性，我们可以使用 functools.wraps（） 作为包装函数的装饰器 。

from functools import wraps

def a_decorator(func): @wraps(func) def wrapper(*args, **kwargs): """A wrapper function""" # Extend some capabilities of func func() return wrapper @a_decorator def first_function(): """This is docstring for first function""" print("first function") @a_decorator def second_function(a): """This is docstring for second function""" print("second function") print(first_function.name) print(first_function.doc) print(second_function.name) print(second_function.doc)

**Output:**输出：

first_function  
This is docstring for first function  
second_function  
This is docstring for second function