Python装饰器使用示例及实际应用例子与应用

我不是女神ヾ 2022-05-31 14:25 261阅读 0赞

这篇文章主要介绍了Python装饰器使用示例及实际应用例子,本文给出了斐波拉契数列、注册回调函数、mysql封装、线程异步等实际使用示例,需要的朋友可以参考下

**测试1**

deco运行，但myfunc并没有运行

复制代码代码如下:

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

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

![20153695110846.png_20152695119][]

**测试2**

需要的deco中调用myfunc，这样才可以执行

复制代码代码如下:

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

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

![20153695130082.png_20152695139][]

**测试3**

@函数名 但是它执行了两次

复制代码代码如下:

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

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

myfunc()

![20153695148926.png_20152695153][]

**测试4**

这样装饰才行

复制代码代码如下:

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

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

![20153695201859.png_2015269527][]

**测试5**

@带参数，使用嵌套的方法

复制代码代码如下:

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()

![20153695221825.png_20152695229][]

**测试6**

函数参数传递

复制代码代码如下:

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')

![20153695238354.png_20152695245][]

**测试7**

未知参数个数

复制代码代码如下:

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')

![20153695256132.png_2015269533][]

**测试8**

class作为修饰器

复制代码代码如下:

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()

![20153695316631.png_20152695322][]

**测试9**

复制代码代码如下:

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()

![20153695335706.png_20152695342][]

**实例**

**给函数做缓存 --- 斐波拉契数列**

复制代码代码如下:

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)

**注册回调函数 --- web请求回调**

复制代码代码如下:

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封装 -- 很好用**

复制代码代码如下:

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):  
    ... ...  
    ... ..

**线程异步**

复制代码代码如下:

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()

[20153695110846.png_20152695119]: http://files.jb51.net/file_images/article/201503/20153695110846.png?20152695119
[20153695130082.png_20152695139]: http://files.jb51.net/file_images/article/201503/20153695130082.png?20152695139
[20153695148926.png_20152695153]: http://files.jb51.net/file_images/article/201503/20153695148926.png?20152695153
[20153695201859.png_2015269527]: http://files.jb51.net/file_images/article/201503/20153695201859.png?2015269527
[20153695221825.png_20152695229]: http://files.jb51.net/file_images/article/201503/20153695221825.png?20152695229
[20153695238354.png_20152695245]: http://files.jb51.net/file_images/article/201503/20153695238354.png?20152695245
[20153695256132.png_2015269533]: http://files.jb51.net/file_images/article/201503/20153695256132.png?2015269533
[20153695316631.png_20152695322]: http://files.jb51.net/file_images/article/201503/20153695316631.png?20152695322
[20153695335706.png_20152695342]: http://files.jb51.net/file_images/article/201503/20153695335706.png?20152695342