First, the decorator:
Essentially function, function: to add additional functionality to other functions
in principle:
1. The decorative function can make changes to the source code
2. You can not modify the function is called modified
A simple decorator
import time
def timmer(func):
def wrapper(*args, **kwargs):
start_time = time.time()
res = func(*args, **kwargs)
stop_time = time.time()
print('函数运行的时间%s'%(stop_time - start_time))
return res
return wrapper
@timmer
def cal(l):
res = 0
for i in l:
time.sleep(0.01)
res += i
return res
ret = cal(range(200))
print(ret)
Second, the decorator's knowledge base
Higher-order function decorator = + + nested closure function
Higher-order function definition:
1. The function received parameter is a function name
2. The return value of the function is a function name
3. satisfies a condition of any of the above, higher order functions can be called
Analog decorator with higher-order functions:
The results run more than once
Time Import
DEF foo ():
the time.sleep (. 3)
Print ( 'from foo')
DEF Timmer (FUNC):
START_TIME the time.time = ()
FUNC ()
stop_time the time.time = ()
Print ( 'run time function S is the% '% (stop_time - START_TIME))
return FUNC
foo = Timmer (foo)
foo ()
Third, the nested functions and closures
Nesting is, re-defined functions in the function
Closure: closing -----> ----- variable packet encapsulated> a function layer
Each package variable start looking for that layer itself began to look for, find and then can not find from the outer layer
Key: function that is variable
DEF Father (name):
DEF Son ():
Print ( 'my father is% S'% name)
DEF Grandson ():
name = 'China'
Print ( 'my grandfather% S'% name)
Grandson ()
Son ()
Father ( 'Henan')
Decorative frame
Timmer DEF (FUNC):
DEF wrapper ():
# add functionality
FUNC ()
return wrapper
The decorator supplement shelf
Time Import
DEF Timmer (FUNC):
DEF warpper ():
# increase functionality
START_TIME the time.time = ()
FUNC ()
stop_time the time.time = ()
Print ( 'run time was S%'% (stop_time - START_TIME))
return wrapper
DEF Test ():
the time.sleep (2)
Print ( 'Test function is finished running')
RES = Timmer (Test) # returns the address of the wrapper
res () # wrapper is performed ()
As can be seen, as long as the function of the last two lines of code to a function of the received value: test
Namely :
test= timmer(test) test()
Decorator look in line with the principle of
But each time had to add functionality to a function to rewrite the test = timmer (test), is clearly unreasonable
Therefore, to replace with @timmer test = timmer (test)
Time Import
DEF Timmer (FUNC):
DEF warpper ():
# increase functionality
START_TIME the time.time = ()
FUNC ()
stop_time the time.time = ()
Print ( 'run time was S%'% (stop_time - START_TIME))
return warpper
@timmer # equivalent: = Timmer Test (Test)
DEF Test ():
the time.sleep (2)
Print ( 'Test function is finished running')
Test ()
Four, plus the return value of the decorator
Time Import
DEF Timmer (FUNC):
DEF warpper ():
# increase functionality
START_TIME the time.time = ()
RES = FUNC () # function test performed here, so to receive variables here a return value to the function
stop_time = time .time ()
Print ( 'run time was S%'% (stop_time - START_TIME))
return RES # here to test the return value returned
return warpper
@timmer # equivalent: = Timmer test (test)
DEF test ():
the time.sleep (2)
Print ( 'function test finishes running')
return 'this is a test of the return value of'
a = test ()
Print (a)
Fifth, add parameters decorators
Time Import
DEF Timmer (FUNC):
DEF wrapper (* args, ** kwargs): # accepts any value
# increasing function
START_TIME the time.time = ()
RES = FUNC (* args, ** kwargs) # accept the wrapper value passed intact FUNC
stop_time the time.time = ()
Print ( 'run time was S%'% (stop_time - START_TIME))
return RES
return warpper
@timmer # equivalent: = Timmer Test (Test)
DEF test1 (name, Age, Gander):
the time.sleep (2)
Print ( 'test1 operation results to name% d% s age sex% s'% (name, Age, Gander))
return 'test1 the return value is'
a = test1 ( 'Jinling', 20 is, 'FEMALE')
Print (A)
@timmer
DEF test2 (name, Age):
the time.sleep (. 3)
print ( 'test2 result of the function is named% s age D%'% (name, Age))
return 'test2 This is the return value of'
B = test2 ( 'liuwen', 18 is)
Print (B)
Sixth, to implement a validation decorator
func_ver DEF (FUNC):
DEF wrapper (* args, ** kwargs):
NAME1 the INPUT = ( 'Please enter your user name:')
pd = the INPUT ( 'Please enter your password:')
IF NAME1 == 'PJL' and pd == '123':
FUNC (* args, ** kwargs)
the else:
Print ( 'user name or password is incorrect')
return wrapper
@func_ver
DEF index ():
Print ( 'Welcome to my site')
@func_ver
Home DEF (name):
Print ( '% S Welcome Home'% name)
@func_ver
DEF Secrect (name):
Print ( '% S this is your little secret'% name)
index ()
Home ( 'jinling')
secrect ( 'jining')
