python：functools.partial和functools.wraps使用

python：functools.partial和functools.wraps使用

1 前言

python内置的functools模块，提供了一些非常好用的类或者方法，其中functools.partial和functools.wraps的使用频率较高，本文将针对其分析使用。

2 使用

2.1 functools.partial

functools.partial是提供的工具类，python源码如下（本文参考自python3.9源码）：

class partial:
    """New function with partial application of the given arguments
    and keywords.
    """

    __slots__ = "func", "args", "keywords", "__dict__", "__weakref__"

    def __new__(cls, func, /, *args, **keywords):
        if not callable(func):
            raise TypeError("the first argument must be callable")

        if hasattr(func, "func"):
            args = func.args + args
            keywords = {
   
   **func.keywords, **keywords}
            func = func.func

        self = super(partial, cls).__new__(cls)

        self.func = func
        self.args = args
        self.keywords = keywords
        return self

    def __call__(self, /, *args, **keywords):
        keywords = {
   
   **self.keywords, **keywords}
        return self.func(*self.args, *args, **keywords)

    @recursive_repr()
    def __repr__(self):
        qualname = type(self).__qualname__
        args = [repr(self.func)]
        args.extend(repr(x) for x in self.args)
        args.extend(f"{
     
     k}={
     
     v!r}" for (k, v) in self.keywords.items())
        if type(self).__module__ == "functools":
            return f"functools.{
     
     qualname}({
     
     ', '.join(args)})"
        return f"{
     
     qualname}({
     
     ', '.join(args)})"

    def __reduce__(self):
        return type(self), (self.func,), (self.func, self.args,
               self.keywords or None, self.__dict__ or None)

    def __setstate__(self, state):
        if not isinstance(state, tuple):
            raise TypeError("argument to __setstate__ must be a tuple")
        if len(state) != 4:
            raise TypeError(f"expected 4 items in state, got {
     
     len(state)}")
        func, args, kwds, namespace = state
        if (not callable(func) or not isinstance(args, tuple) or
           (kwds is not None and not isinstance(kwds, dict)) or
           (namespace is not None and not isinstance(namespace, dict))):
            raise TypeError("invalid partial state")

        args = tuple(args) # just in case it's a subclass
        if kwds is None:
            kwds = {
   
   }
        elif type(kwds) is not dict: # XXX does it need to be *exactly* dict?
            kwds = dict(kwds)
        if namespace is None:
            namespace = {
   
   }

        self.__dict__ = namespace
        self.func = func
        self.args = args
        self.keywords = kwds

根据源码，我们以同样的逻辑定义part类（功能类似partial）：

def add(x, y):
    return x + y


class part:
    def __new__(cls, fun