Python decorator use example and actual application example, python example

Python decorator use example and actual application example, python example

Test 1

Deco is running, but myfunc is not running

Copy codeThe Code is as follows:
Def deco (func ):
Print 'before func'
Return func

Def myfunc ():
Print 'myfunc () called'
 
Myfunc = deco (myfunc)

Test 2

Call myfunc in the required deco to execute
Copy codeThe Code is as follows:
Def deco (func ):
Print 'before func'
Func ()
Print 'after func'
Return func

Def myfunc ():
Print 'myfunc () called'
 
Myfunc = deco (myfunc)

Test 3

@ Function name, but it is executed twice

Copy codeThe Code is as follows:
Def deco (func ):
Print 'before func'
Func ()
Print 'after func'
Return func

@ Deco
Def myfunc ():
Print 'myfunc () called'

Myfunc ()

Test 4

This decoration is required.

Copy codeThe Code is as follows:
Def deco (func ):
Def _ deco ():
Print 'before func'
Func ()
Print 'after func'
Return _ deco

@ Deco
Def myfunc ():
Print 'myfunc () called'
 
Myfunc ()

Test 5

@ Use nested methods with Parameters
Copy codeThe Code is as follows:
Def deco (arg ):
Def _ deco (func ):
Print arg
Def _ deco ():
Print 'before func'
Func ()
Print 'after func'
Return _ deco
Return _ deco

@ Deco ('Demo ')
Def myfunc ():
Print 'myfunc () called'
 
Myfunc ()

Test 6

Function parameter transfer
Copy codeThe Code is as follows:
Def deco (arg ):
Def _ deco (func ):
Print arg
Def _ deco (str ):
Print 'before func'
Func (str)
Print 'after func'
Return _ deco
Return _ deco

@ Deco ('Demo ')
Def myfunc (str ):
Print 'myfunc () called', str
 
Myfunc ('hello ')

Test 7

Number of unknown parameters
Copy codeThe Code is as follows:
Def deco (arg ):
Def _ deco (func ):
Print arg
Def _ deco (* args, ** kwargs ):
Print 'before func'
Func (* args, ** kwargs)
Print 'after func'
Return _ deco
Return _ deco

@ Deco ('decode1 ')
Def myfunc1 (str ):
Print 'myfunc1 () called', str

@ Deco ('demo2 ')
Def myfunc2 (str1, str2 ):
Print 'myfunc2 () called', str1, str2
 
Myfunc1 ('hello ')
 
Myfunc2 ('hello', 'World ')

Test 8

Class As Modifier
Copy codeThe Code is as follows:
Class myDecorator (object ):
 
Def _ init _ (self, fn ):
Print "inside myDecorator. _ init __()"
Self. fn = fn
 
Def _ call _ (self ):
Self. fn ()
Print "inside myDecorator. _ call __()"
 
@ MyDecorator
Def aFunction ():
Print "inside aFunction ()"
 
Print "Finished decorating aFunction ()"
 
AFunction ()

Test 9
Copy codeThe Code is as follows:
Class myDecorator (object ):
 
Def _ init _ (self, str ):
Print "inside myDecorator. _ init __()"
Self. str = str
Print self. str
 
Def _ call _ (self, fn ):
Def wrapped (* args, ** kwargs ):
Fn ()
Print "inside myDecorator. _ call __()"
Return wrapped
 
@ MyDecorator ('this is str ')
Def aFunction ():
Print "inside aFunction ()"
 
Print "Finished decorating aFunction ()"
 
AFunction ()

Instance

Caching functions-Fibonacci Series

Copy codeThe Code is as follows:
From functools import wraps
Def memo (fn ):
Cache = {}
Miss = object ()

@ Wraps (fn)
Def wrapper (* args ):
Result = cache. get (args, miss)
If result is miss:
Result = fn (* args)
Cache [args] = result
Return result
 
Return wrapper
 
@ Memo
Def fib (n ):
If n <2:
Return n
Return fib (n-1) + fib (n-2)

Print fib (10)

Register callback function-web Request callback

Copy codeThe Code is as follows:
Class MyApp ():
Def _ init _ (self ):
Self. func_map = {}
 
Def register (self, name ):
Def func_wrapper (func ):
Self. func_map [name] = func
Return func
Return func_wrapper
 
Def call_method (self, name = None ):
Func = self. func_map.get (name, None)
If func is None:
Raise Exception ("No function registered against-" + str (name ))
Return func ()
 
App = MyApp ()
 
@ App. register ('/')
Def main_page_func ():
Return "This is the main page ."
 
@ App. register ('/next_page ')
Def next_page_func ():
Return "This is the next page ."
 
Print app. call_method ('/')
Print app. call_method ('/next_page ')

Mysql encapsulation-Easy to use
Copy codeThe Code is as follows:
Import umysql
From functools import wraps
 
Class Organization aion:
Def _ init _ (self, env ):
If env = "Prod ":
Self. host = "coolshell.cn"
Self. port = 3306
Self. db = "coolshell"
Self. user = "coolshell"
Self. passwd = "fuckgfw"
Elif env = "Test ":
Self. host = 'localhost'
Self. port = 3300
Self. user = 'coolshell'
Self. db = 'coolshell'
Self. passwd = 'fuckgfw'
 
Def mysql (SQL ):
 
_ Conf = paiaion (env = "Prod ")
 
Def on_ SQL _error (err ):
Print err
Sys. exit (-1)
 
Def handle_ SQL _result (rs ):
If rs. rows> 0:
Fieldnames = [f [0] for f in rs. fields]
Return [dict (zip (fieldnames, r) for r in rs. rows]
Else:
Return []
 
Def decorator (fn ):
@ Wraps (fn)
Def wrapper (* args, ** kwargs ):
Mysqlconn = umysql. Connection ()
Mysqlconn. settimeout (5)
Mysqlconn. connect (_ conf. host, _ conf. port, _ conf. user ,\
_ Conf. passwd, _ conf. db, True, 'utf8 ')
Try:
Rs = mysqlconn. query (SQL ,{})
Failed t umysql. Error as e:
On_ SQL _error (e)
 
Data = handle_ SQL _result (rs)
Kwargs ["data"] = data
Result = fn (* args, ** kwargs)
Mysqlconn. close ()
Return result
Return wrapper
 
Return decorator
 
 
@ Mysql (SQL = "select * from coolshell ")
Def get_coolshell (data ):
......
.....

Asynchronous thread
Copy codeThe Code is as follows:
From threading import Thread
From functools import wraps
 
Def async (func ):
@ Wraps (func)
Def async_func (* args, ** kwargs ):
Func_hl = Thread (target = func, args = args, kwargs = kwargs)
Func_hl.start ()
Return func_hl
 
Return async_func
 
If _ name _ = '_ main __':
From time import sleep
 
@ Async
Def print_somedata ():
Print 'starting print_somedata'
Sleep (2)
Print 'print _ somedata: 2 sec passed'
Sleep (2)
Print 'print _ somedata: 2 sec passed'
Sleep (2)
Print 'finished print_somedata'
 
Def main ():
Print_somedata ()
Print 'Back in main'
Print_somedata ()
Print 'Back in main'
 
Main ()