python - 第一次使用装饰器，我错过了什么？

Question

class User:
    def __init__(self):
       self.score = 0
       self.wins = 0
       self.losses = 0


    def tally(self, func):
        def wrapper_function(w):
            print("Wins: {}\nLosses: {}\nTotal Score: {}".format(self.wins, self.losses, self.score))
            return func(w)
        return wrapper_function()

    @tally
    def record_win(self, w=1):
        self.wins += w


user1 = User()
user1.record_win()

我得到的错误是:TypeError: tally() missing 1 required positional argument: 'func'

编辑 这篇文章不同于here因为在那篇文章中装饰器函数不是实例方法..我现在看到它增加了一些特殊的要求。

Answer 1

你的问题是你将 tally 定义为一个实例方法，但它实际上只是一个装饰函数(它不能以任何合理的方式在实例上调用)。如果你坚持，你仍然可以在类中定义它(它只是对实例没用)，你只需要让它接受一个参数(要包装的函数)，没有 self，并使 < em>wrapper 接受 self(同时将任何提供的参数传递给包装函数):

class User:
    # ... other methods unchanged ...
    def tally(func):
        def wrapper_function(self, *args, **kwargs):  # Accept self + arbitrary arguments to make decorator useable on more functions
            print("Wins: {}\nLosses: {}\nTotal Score: {}".format(self.wins, self.losses, self.score))
            return func(self, *args, **kwargs)  # Pass along self to wrapped function along with arbitrary arguments
        return wrapper_function                 # Don't call the wrapper function; you have to return it so it replaces the decorated function
    
    @tally
    def record_win(self, w=1):
        self.wins += w

    # Optionally, once tally is no longer needed for new methods, but before dedenting out of class definition, do:
    del tally
    # so it won't stick around to appear as a possible method to call on instances
    # It's done all the work it needs to do after all

删除 w 参数以支持 *args, **kwargs 意味着您不需要专注于特定的函数原型(prototype)，也不需要复制函数的默认值你正在包装(如果他们不传递参数，默认值将自动使用)。