十. Python基础(10)--装饰器
1 ● 装饰器
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A decorator is a function that take a function as an argument and return a function. We can use a decorator to extend the functionality of an existing function without changing its source. Decorators are syntactic sugar. 装饰器是一个函数, 它接受一个函数作为实参并且返回一个函数. 我们可以用装饰器来扩充一个已经存在的函数的功能, 但又不修改其源码. 装饰器是一种语法糖(syntactic sugar). ※ The "@" symbol indicates to the parser that we're using a decorator while the decorator function name references a function by that name. ※ |
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※ A decorator in Python is any callable Python object that is used to modify a function or a class. A reference to a function "func" or a class "C" is passed to a decorator and the decorator returns a modified function or class. The modified functions or classes usually contain calls to the original function "func" or class "C". |
2 ● 装饰器的模板
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def wrapper(func): # wrapper是装饰器的名字 def inner(*args, **kwargs): print("被装饰的函数执行之前你要做的事.") ret = func(*args, **kwargs) # 被装饰的函数执行, 返回值为None也写出来 print("被装饰的函数执行之后你要做的事.") return ret # ret有可能是None, 并且没有变量接收 return inner
@wrapper # 相当于welcome = wrapper(welcome) def welcome(name): # welcome是被装饰的函数 print('Welcome:%s!'%name)
@wrapper def home(): # home是被装饰的函数 print('欢迎来到home页!')
welcome("Arroz") print("===============================") home() |
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参见: http://blog.csdn.net/qq_34409701/article/details/51589736 |
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def wrapper(func): def inner(*args, **kwargs): print("AAAAAAA") print(func(*args, **kwargs)) return inner
@wrapper def f1(): return "f1"
f1()
''' AAAAAAA f1 ''' |
知识补充:
1 ● eval()函数
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if name in locals(): return eval(name)(*args) |
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※ name是函数名, 后面的形参需要和一般函数名一样带括号(*args) |
2 ● 斐波那契数列停止的情况:
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# ① 长度小于多少 ''' l=[1,1] while len(l) < 20: l.append(l[-1]+l[-2]) print(l) ''' # ② 最后一个数小于多少 ''' l = [1,1] while l[-1] < 40000: l.append(l[-1] + l[-2]) print(l) ''' |