Python装饰器使用示例及实际应用例子

测试1

deco运行，但myfunc并没有运行

def deco(func):

 print 'before func'

 return func

def myfunc():

 print 'myfunc() called'



myfunc = deco(myfunc)

测试2

需要的deco中调用myfunc，这样才可以执行

def deco(func):

 print 'before func'

 func()

 print 'after func'

 return func

def myfunc():

 print 'myfunc() called'



myfunc = deco(myfunc)

测试3

@函数名 但是它执行了两次

def deco(func):

 print 'before func'

 func()

 print 'after func'

 return func

@deco

def myfunc():

 print 'myfunc() called'
myfunc()

测试4

这样装饰才行

def deco(func):

 def _deco():

 print 'before func'

 func()

 print 'after func'

 return _deco

@deco

def myfunc():

 print 'myfunc() called'



myfunc()

测试5

@带参数，使用嵌套的方法

def deco(arg):

 def _deco(func):

 print arg

 def __deco():

 print 'before func'

 func()

 print 'after func'

 return __deco

 return _deco

@deco('deco')

def myfunc():

 print 'myfunc() called'



myfunc()

测试6

函数参数传递

def deco(arg):

 def _deco(func):

 print arg

 def __deco(str):

 print 'before func'

 func(str)

 print 'after func'

 return __deco

 return _deco

@deco('deco')

def myfunc(str):

 print 'myfunc() called ', str



myfunc('hello')

测试7

未知参数个数

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('deco1')

def myfunc1(str):

 print 'myfunc1() called ', str
@deco('deco2')

def myfunc2(str1,str2):

 print 'myfunc2() called ', str1, str2



myfunc1('hello')



myfunc2('hello', 'world')

测试8

class作为修饰器

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()

测试9

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()

实例

给函数做缓存 --- 斐波拉契数列

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)

注册回调函数 --- web请求回调

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封装 -- 很好用

import umysql

from functools import wraps



class Configuraion:

 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 = Configuraion(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, {}) 

 except 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):

 ... ...

 ... ..

线程异步

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()

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