Python装饰器的专业解释

装饰器，其实是用到了闭包的原理来进行操作的。

单个装饰器：

以下是一个简单的例子：

def outer(func):
    print("OUTER enter ...")

    def wrapper(*args, **kwargs):
        print("调用之前......")
        result = func(*args, **kwargs)
        print("调用之后......")
        return result

    print("OUTER leave ...")
    return wrapper


@outer
def my_hello():
    print("hello world")

上面的代码可以运行出结果：

这个时候就会把这个闭包创建出来。

当我们调用my_hello函数的时候，会进行执行wrapper里的代码：

def outer(func):
    print("OUTER enter ...")

    def wrapper(*args, **kwargs):
        print("调用之前......")
        result = func(*args, **kwargs)
        print("调用之后......")
        return result

    print("OUTER leave ...")
    return wrapper


@outer
def my_hello():
    print("hello world")


my_hello()

调用原理：

等价于：

def outer(func):
    print("OUTER enter ...")

    def wrapper(*args, **kwargs):
        print("调用之前......")
        result = func(*args, **kwargs)
        print("调用之后......")
        return result

    print("OUTER leave ...")
    return wrapper


# @outer
def my_hello():
    print("hello world")


my_hello = outer(my_hello)
my_hello()

多重装饰器修饰：

def outer1(func):
    print("OUTER enter ...1")

    def wrapper(*args, **kwargs):
        print("调用之前......1")
        result = func(*args, **kwargs)
        print("调用之后......1")
        return result

    print("OUTER leave ...1")
    return wrapper


def outer2(func):
    print("OUTER enter ...2")

    def wrapper(*args, **kwargs):
        print("调用之前......2")
        result = func(*args, **kwargs)
        print("调用之后......2")
        return result

    print("OUTER leave ...2")
    return wrapper


@outer1
@outer2
def my_hello():
    print("hello world")

打印的结果如下：

调用的时候：

def outer1(func):
    print("OUTER enter ...1")

    def wrapper(*args, **kwargs):
        print("调用之前......1")
        result = func(*args, **kwargs)
        print("调用之后......1")
        return result

    print("OUTER leave ...1")
    return wrapper


def outer2(func):
    print("OUTER enter ...2")

    def wrapper(*args, **kwargs):
        print("调用之前......2")
        result = func(*args, **kwargs)
        print("调用之后......2")
        return result

    print("OUTER leave ...2")
    return wrapper


@outer1
@outer2
def my_hello():
    print("hello world")


my_hello()

运行结果为：

调用原理：

def outer1(func):
    print("OUTER enter ...1")

    def wrapper(*args, **kwargs):
        print("调用之前......1")
        result = func(*args, **kwargs)
        print("调用之后......1")
        return result

    print("OUTER leave ...1")
    return wrapper


def outer2(func):
    print("OUTER enter ...2")

    def wrapper(*args, **kwargs):
        print("调用之前......2")
        result = func(*args, **kwargs)
        print("调用之后......2")
        return result

    print("OUTER leave ...2")
    return wrapper


# @outer1
# @outer2
def my_hello():
    print("hello world")


my_hello = outer2(my_hello)
my_hello = outer1(my_hello)

my_hello()

运行结果如下：