python: decorator study notes

Decorator: essentially a function 
function :( other decorative function) is to add additional functionality to other function 
principles: 1. Do not modify the source code to be decorated function 
     2. You can not modify the way calls are decorated function 
     
to achieve decorator knowledge base: 
1, i.e. the function "variable" 
2. higher order functions: 
    a: to a function name as an argument passed to another function (not to be modified to add decorative features case where the function of the source code) 
    B: returns the value It contains the function name (not modify function is called) 
3, + higher order function nested function = decorator

import time

def timer(func):
    print("x1")
    def deco(*args,**kwargs):
        print("x2")
        start_time = time.time()
        back = func(*args,**kwargs)
        stop_time = time.time()
        print("The run time of func is %s " % (stop_time - start_time))
        return back
    return deco

@timer    # test1 = timer(test1)
def test1():
    time.sleep(1)
    print("in the test1")


@timer   #test2 = timer(test2)
def test2(name,age):
    time.sleep(1)
    print("in the test2 is %s and %s"%(name,age))
    return "I "

test1()
#print(test2("Huan",22))
#print("\033[33;1m xxxxxx \033[0m")

Decorator

 

Running process:

　　First declare the function timer, then after encountering @timer, it will function into the timer. Then execute print ( "x1"), and declared inside a function deco, but not executed, the return deco test1 = deco, wait until the call test1 (), in fact, call timer in the deco. Achieved without modifying the source code, the source code does not change the way calls.