python进阶19装饰器和闭包

>>> def outer():
...     x = 1
...     def inner():
...         print x # 1
...     inner() # 2
...
>>> outer()

>>> def outer():
...     x = 1
...     def inner():
...         print x # 1
...     return inner
>>> foo = outer()
>>> foo.func_closure # doctest: +ELLIPSIS
(\<cell at 0x.... int object at 0x...>,)

>>> def outer(x):
...     def inner():
...         print x # 1
...     return inner
>>> print1 = outer(1)
>>> print2 = outer(2)
>>> print1()
1
>>> print2()
2

def multipliers():
    return [lambda x: i * x for i in range(4)]
print([m(2) for m in multipliers()])

#生成器
def multipliers():
    return (lambda x: i * x for i in range(4))
print([m(2) for m in multipliers()])  

#匿名函数的入参绑定
def multipliers():
    return [lambda x, j=i: j * x for i in range(4)]
print([m(2) for m in multipliers()])  

# 偏函数
from functools import partial
def multipliers_ch2():
    return [partial(lambda m, x: m * x, i) for i in range(4)]
print([m(2) for m in multipliers()])  

# yield生成器
def multipliers_ch3():
    for m in range(4):
        yield lambda x: m * x
print([m(2) for m in multipliers()])

>>> def outer(some_func):  
...     def inner():  
...         print "before some_func"  
...         ret = some_func() # 1  
...         return ret + 1  
...     return inner  
>>> def foo():  
...     return 1  
>>> decorated = outer(foo) # 2  
>>> decorated()  
before some_func  
2

>>> class Coordinate(object):  
...     def __init__(self, x, y):  
...         self.x = x  
...         self.y = y  
...     def __repr__(self)  
...         return "Coord:" + str(self.__dict__)  
>>> def add(a, b):  
...     return Coordinate(a.x + b.x, a.y + b.y)  
>>> def sub(a, b):  
...      return Coordinate(a.x - b.x, a.y - b.y)  
>>> one = Coordinate(100, 200)  
>>> two = Coordinate(300, 200)  
>>> add(one, two)  
Coord:{'y': 400, 'x': 400}

>>> def wrapper(func):  
...     def checker(a, b): # 1  
...         if a.x < 0 or a.y < 0:  
...             a = Coordinate(a.x if a.x > 0 else 0, a.y if a.y > 0 else 0)  
...         if b.x < 0 or b.y < 0:  
...             b = Coordinate(b.x if b.x > 0 else 0, b.y if b.y > 0 else 0)  
...         ret = func(a, b)  
...         if ret.x < 0 or ret.y < 0:  
...             ret = Coordinate(ret.x if ret.x > 0 else 0, ret.y if re> 0 else 0)  
...         return ret  
...     return checker  
>>> add = wrapper(add)  
>>> sub = wrapper(sub)  
>>> sub(one, two)  
Coord: {'y': 0, 'x': 0}  
>>> add(one, three)  
Coord: {'y': 200, 'x': 100}

# 小明，中国人
@say_hello("china")
def xiaoming():
    pass

# jack，美国人
@say_hello("america")
def jack():
    pass
那我们如果实现这个装饰器，让其可以实现 传参 呢？

会比较复杂，需要两层嵌套。

def say_hello(contry):
    def wrapper(func):
        def deco(*args, **kwargs):
            if contry == "china":
                print("你好!")
            elif contry == "america":
                print('hello.')
            else:
                return

            # 真正执行函数的地方
            func(*args, **kwargs)
        return deco
    return wrapper

来执行一下  
xiaoming()
print("------------")
jack()

你好!
------------
hello.

import time
import functools

class DelayFunc:
    def __init__(self,  duration, func):
        self.duration = duration
        self.func = func

    def __call__(self, *args, **kwargs):
        print(f'Wait for {self.duration} seconds...')
        time.sleep(self.duration)
        return self.func(*args, **kwargs)

    def eager_call(self, *args, **kwargs):
        print('Call without delay')
        return self.func(*args, **kwargs)

def delay(duration):
    """
    装饰器：推迟某个函数的执行。
    同时提供 .eager_call 方法立即执行
    """
    # 此处为了避免定义额外函数，
    # 直接使用 functools.partial 帮助构造 DelayFunc 实例
    return functools.partial(DelayFunc, duration)
我们的业务函数很简单，就是相加

@delay(duration=2)
def add(a, b):
    return a+b

>>> add    # 可见 add 变成了 Delay 的实例
<__main__.DelayFunc object at 0x107bd0be0>
>>>
>>> add(3,5)  # 直接调用实例，进入 __call__
Wait for 2 seconds...
8
>>>
>>> add.func # 实现实例方法
<function add at 0x107bef1e0>