装饰器是修改其他函数的函数。好处是可以让你的函数更简洁。
一步步理解这个概念：
一、一切皆对象。
def hi(name="yasoob"): return "hi " + name print(hi()) # output: ‘hi yasoob‘ # 我们甚至可以将一个函数赋值给一个变量，比如 greet = hi # 我们这里没有在使用小括号，因为我们并不是在调用hi函数 # 而是在将它放在greet变量里头。我们尝试运行下这个 print(greet()) # output: ‘hi yasoob‘ # 如果我们删掉旧的hi函数，看看会发生什么！ del hi print(hi()) #outputs: NameError print(greet()) #outputs: ‘hi yasoob‘
二、函数中定义函数
def hi(name="yasoob"): print("now you are inside the hi() function") def greet(): return "now you are in the greet() function" def welcome(): return "now you are in the welcome() function" print(greet()) print(welcome()) print("now you are back in the hi() function") hi() #output:now you are inside the hi() function # now you are in the greet() function # now you are in the welcome() function # now you are back in the hi() function # 上面展示了无论何时你调用hi(), greet()和welcome()将会同时被调用。 # 然后greet()和welcome()函数在hi()函数之外是不能访问的，比如： greet() #outputs: NameError: name ‘greet‘ is not defined
三、函数中返回函数
def hi(name="yasoob"): def greet(): return "now you are in the greet() function" def welcome(): return "now you are in the welcome() function" if name == "yasoob": return greet else: return welcome a = hi() print(a) #outputs: <function greet at 0x7f2143c01500> #上面清晰地展示了`a`现在指向到hi()函数中的greet()函数 #现在试试这个 print(a()) #outputs: now you are in the greet() function
四、函数作为参数传递
def hi(): return "hi yasoob!" def doSomethingBeforeHi(func): print("I am doing some boring work before executing hi()") print(func()) doSomethingBeforeHi(hi) #outputs:I am doing some boring work before executing hi() # hi yasoob!
五、第一个装饰器
def a_new_decorator(a_func): def wrapTheFunction(): print("I am doing some boring work before executing a_func()") a_func() print("I am doing some boring work after executing a_func()") return wrapTheFunction def a_function_requiring_decoration(): print("I am the function which needs some decoration to remove my foul smell") a_function_requiring_decoration() #outputs: "I am the function which needs some decoration to remove my foul smell" a_function_requiring_decoration = a_new_decorator(a_function_requiring_decoration) #now a_function_requiring_decoration is wrapped by wrapTheFunction() a_function_requiring_decoration() #outputs:I am doing some boring work before executing a_func() # I am the function which needs some decoration to remove my foul smell # I am doing some boring work after executing a_func()
六、使用@符号
@a_new_decorator def a_function_requiring_decoration(): """Hey you! Decorate me!""" print("I am the function which needs some decoration to " "remove my foul smell") a_function_requiring_decoration() #outputs: I am doing some boring work before executing a_func() # I am the function which needs some decoration to remove my foul smell # I am doing some boring work after executing a_func() #the @a_new_decorator is just a short way of saying: a_function_requiring_decoration = a_new_decorator(a_function_requiring_decoration)
七、遇到问题
print(a_function_requiring_decoration.__name__) # Output: wrapTheFunction
八、解决问题
from functools import wraps def a_new_decorator(a_func): @wraps(a_func) def wrapTheFunction(): print("I am doing some boring work before executing a_func()") a_func() print("I am doing some boring work after executing a_func()") return wrapTheFunction @a_new_decorator def a_function_requiring_decoration(): """Hey yo! Decorate me!""" print("I am the function which needs some decoration to " "remove my foul smell") print(a_function_requiring_decoration.__name__) # Output: a_function_requiring_decoration
九、蓝本规范
from functools import wraps def decorator_name(f): @wraps(f) def decorated(*args, **kwargs): if not can_run: return "Function will not run" return f(*args, **kwargs) return decorated @decorator_name def func(): return("Function is running") can_run = True print(func()) # Output: Function is running can_run = False print(func()) # Output: Function will not run
十、使用场景
（1）授权（Authorization）
from functools import wraps def requires_auth(f): @wraps(f) def decorated(*args, **kwargs): auth = request.authorization if not auth or not check_auth(auth.username, auth.password): authenticate() return f(*args, **kwargs) return decorated
原文：https://www.cnblogs.com/python-xuehb/p/11857532.html
