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()