Python裝飾器使用示例及實際應用例子

更新時間：2015年03月06日 09:57:06 投稿：junjie

這篇文章主要介紹了Python裝飾器使用示例及實際應用例子,本文給出了斐波拉契數(shù)列、注冊回調(diào)函數(shù)、mysql封裝、線程異步等實際使用示例,需要的朋友可以參考下

測試1

deco運行，但myfunc并沒有運行

復制代碼代碼如下:

def deco(func):
print 'before func'
return func

def myfunc():
print 'myfunc() called'

myfunc = deco(myfunc)

測試2

需要的deco中調(diào)用myfunc，這樣才可以執(zhí)行

復制代碼代碼如下:

def deco(func):
    print 'before func'
    func()
    print 'after func'
    return func

def myfunc():
print 'myfunc() called'

myfunc = deco(myfunc)

測試3

@函數(shù)名但是它執(zhí)行了兩次

復制代碼代碼如下:

def deco(func):
    print 'before func'
    func()
    print 'after func'
    return func

@deco
def myfunc():
print 'myfunc() called'

myfunc()

測試4

這樣裝飾才行

復制代碼代碼如下:

def deco(func):
    def _deco():
        print 'before func'
        func()
        print 'after func'
    return _deco

@deco
def myfunc():
print 'myfunc() called'

myfunc()

測試5

@帶參數(shù)，使用嵌套的方法

復制代碼代碼如下:

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()

測試6

函數(shù)參數(shù)傳遞

復制代碼代碼如下:

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')

測試7

未知參數(shù)個數(shù)

復制代碼代碼如下:

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')

測試8

class作為修飾器

復制代碼代碼如下:

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()

測試9

復制代碼代碼如下:

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()

實例

給函數(shù)做緩存 --- 斐波拉契數(shù)列

復制代碼代碼如下:

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)

注冊回調(diào)函數(shù) --- web請求回調(diào)

復制代碼代碼如下:

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封裝 -- 很好用

復制代碼代碼如下:

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):

    ... ...

    ... ..

線程異步

復制代碼代碼如下:

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()