装饰器中的这个函数在 Python 中是如何工作的？

Question

def title_decorator(print_name_function):
#in addition to printing name it will print a title
    def wrapper():
        #it will wrap print_my_name with some functionality
        print("Professor:")
        print_name_function() #<----- QUESTION HERE
        #wrapper will print out professor and then call print_name_function
    return wrapper

def print_my_name():
    print("Joseph")

def print_mike():
    print("Mike")

decorated_function = title_decorator(print_mike)
#calling decorator function, passing in print_my_name

decorated_function
decorated_function()

在def wrapper()我们有print_name_function() ，它是如何工作的，为什么我们在这里包含() ？

我看到我们正在将print_name_function传入title_decorator

但我真的不明白它是如何包含在def wrapper()以及在print_name_function()后面包含()意味着什么

Answer 1

把装饰器想象成一个返回另一个函数的函数。 您想要做的是在不更改其实现的情况下向函数添加行为。

在实践中，装饰器具有以下行为。

def title_decorator(print_name_function):

    # now your decorator have a local variable (print_name_function) 
    # in that function scope that variable is a reference to another 
    # function

    def wrapper():
        # now you write a function that do something

        print("Professor:")
        print_name_function() # here you function is calling a scope 
                              # variable that by the way is another 
                              # function. See that the scope of this 
                              # variable is *title_decorator*


    # now instead to return your argument function you return another
    # with some other behavior
    return wrapper

OBS：当包装器调用函数时，这是对对象的引用。 保持这就是头脑

Answer 2

简单的装饰器函数用于增强函数的功能。 阅读我的代码的注释希望你理解这一点。

def title_decorator(print_name_function):   # this function take one function as argument
    def wrapper(): # Here is Rapper function
        print("Professor:")
        print_name_function() #(<----- QUESTION HERE) Answer-----> We are calling the same function because without calling
                                    # doesn't work, basically the function we passed in title_decorator() calls print_name_function()
                                    # inside wrapper function,
        #wrapper will print out professor and then call print_name_function
    return wrapper

def print_my_name():
    print("Joseph")

def print_mike():
    print("Mike")


decorated_function = title_decorator(print_mike)    # Here you calling your function and give print_mike() function as an argument
                        # store it's returning value in variable named as decorated_function, so first time your decorator returns
                        # called wrapper() function
decorated_function()   # and then your variable become decorated_function is working as a function that's why you calling this```