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
