python裝飾器詳解，最全的python解釋器

函數式編程複習：

def map_test(func,array): array_new=[] for i in array: array_new.append(func(i)) return array_new print map_test(lambda x:x**2,range(10)) print map(lambda x:x**2,range(10)) def odd(num): return num % 2 def filter_test(func,array): array_new=[] for i in array: if func(i): array_new.append(i) return array_new print filter_test(odd,range(10)) print filter(odd,range(10)) def reduce_test(func,array,init): l=list(array) if init is None: res=l.pop(0) else: res=init for i in l: res=func(res,i) return res print reduce_test(lambda x,y:x+y,range(100),10) print reduce(lambda x,y:x+y,range(100),10)

 

 

python裝飾器

一:函數調用順序：其餘高級語言相似,Python 不容許在函數未聲明以前,對其進行引用或者調用
錯誤示範：

def foo(): print 'in the foo' bar() foo() 報錯： in the foo Traceback (most recent call last): File "<pyshell#13>", line 1, in <module> foo() File "<pyshell#12>", line 3, in foo bar() NameError: global name 'bar' is not defined

 

def foo(): print 'foo' bar() foo() def bar(): print 'bar' 報錯：NameError: global name 'bar' is not defined

 

正確示範:(注意，python爲解釋執行，函數foo在調用前已經聲明瞭bar和foo，因此bar和foo無順序之分)

def bar(): print 'in the bar' def foo(): print 'in the foo' bar() foo() def foo(): print 'in the foo' bar() def bar(): print 'in the bar' foo()

 

 

 

二：高階函數

知足下列條件之一就可成函數爲高階函數

1. 某一函數當作參數傳入另外一個函數中

2. 函數的返回值包含n個函數,n>0

    

高階函數示範：

def bar(): print 'in the bar' def foo(func): res=func() return res foo(bar)

 

高階函數的牛逼之處：

def foo(func): return func print 'Function body is %s' %(foo(bar)) print 'Function name is %s' %(foo(bar).func_name) foo(bar)() #foo(bar)() 等同於bar=foo(bar)而後bar() bar=foo(bar) bar()

 

 

三：內嵌函數和變量做用域：

定義：在一個函數體內建立另一個函數，這種函數就叫內嵌函數(基於python支持靜態嵌套域)

函數嵌套示範：

def foo(): def bar(): print 'in the bar' bar() foo() # bar()

 

局部做用域和全局做用域的訪問順序

x=0 def grandpa(): # x=1 def dad(): x=2 def son(): x=3 print x son() dad() grandpa()

 

 

局部變量修改對全局變量的影響

y=10 # def test(): # y+=1 # print y def test(): # global y y=2 print y test() print y def dad(): m=1 def son(): n=2 print '--->',m + n print '-->',m son() dad()

 

 

四：閉包：若是在一個內部函數裏，對在外部做用域(但不是在全局做用域）的變量進行引用，那麼內部函數就被認爲是 closure

def counter(start_num=0): count=[start_num] def incr(): count[0]+=1 return count[0] return incr print counter() print counter()() print counter()() c=counter() print c() print c()

 

 

五：內嵌函數+高階函數+閉包=》裝飾器

預熱兩個範例:

範例一：函數參數固定

def decorartor(func): def wrapper(n): print 'starting' func(n) print 'stopping' return wrapper def test(n): print 'in the test arg is %s' %n decorartor(test)('alex')

 

 

範例二：函數參數不固定

def decorartor(func): def wrapper(*args,**kwargs): print 'starting' func(*args,**kwargs) print 'stopping' return wrapper def test(n,x=1): print 'in the test arg is %s' %n decorartor(test)('alex',x=2)

 

1. 無參裝飾器

import time def decorator(func): def wrapper(*args,**kwargs): start=time.time() func(*args,**kwargs) stop=time.time() print 'run time is %s ' %(stop-start) print timeout return wrapper @decorator def test(list_test): for i in list_test: time.sleep(0.1) print '-'*20,i #decorator(test)(range(10)) test(range(10))

 

2. 有參裝飾器

import time def timer(timeout=0): def decorator(func): def wrapper(*args,**kwargs): start=time.time() func(*args,**kwargs) stop=time.time() print 'run time is %s ' %(stop-start) print timeout return wrapper return decorator @timer(2) def test(list_test): for i in list_test: time.sleep(0.1) print '-'*20,i #timer(timeout=10)(test)(range(10)) test(range(10))

 

 

六：裝飾器應用案例：

裝飾器功能：函數超時則終止

# -*- coding: utf-8 -*- from threading import Thread import time class TimeoutException(Exception): pass ThreadStop = Thread._Thread__stop#獲取私有函數 def timelimited(timeout): def decorator(function): def decorator2(*args,**kwargs): class TimeLimited(Thread): def __init__(self,_error= None,): Thread.__init__(self) self._error = _error def run(self): try: self.result = function(*args,**kwargs) except Exception,e: self._error =e def _stop(self): if self.isAlive(): ThreadStop(self) t = TimeLimited() t.start() t.join(timeout) if isinstance(t._error,TimeoutException): t._stop() raise TimeoutException('timeout for %s' % (repr(function))) if t.isAlive(): t._stop() raise TimeoutException('timeout for %s' % (repr(function))) if t._error is None: return t.result return decorator2 return decorator @timelimited(2) def fn_1(secs): time.sleep(secs) return 'Finished' if __name__ == "__main__": print fn_1(4)

 https://www.cnblogs.com/java-a/p/13269346.html