python装饰器详解，最全的python解释器
函数式编程复习：
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装饰器
一:函数调用顺序：其他高级语言类似,Python 不允许在函数未声明之前,对其进行引用或者调用
错误示范：
def foo():
print 'in the foo'
bar()
foo()
报错：
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 defineddef foo():
print 'foo'
bar()
foo()
def bar():
print 'bar'
报错：NameError: global name 'bar' is not defined正确示范:(注意，python为解释执行，函数foo在调用前已经声明了bar和foo，所以bar和foo无顺序之分)
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：高阶函数
满足下列条件之一就可成函数为高阶函数
-
某一函数当做参数传入另一个函数中
-
函数的返回值包含n个函数,n>0
高阶函数示范：
def bar():
print 'in the bar'
def foo(func):
res=func()
return res
foo(bar)高阶函数的牛逼之处：
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)() 等同于bar=foo(bar)然后bar()
bar=foo(bar)
bar()
三：内嵌函数和变量作用域：
定义：在一个函数体内创建另外一个函数，这种函数就叫内嵌函数(基于python支持静态嵌套域)
函数嵌套示范：
def foo():
def bar():
print 'in the bar'
bar()
foo()
# bar()局部作用域和全局作用域的访问顺序
x=0
def grandpa():
# x=1
def dad():
x=2
def son():
x=3
print x
son()
dad()
grandpa()
局部变量修改对全局变量的影响
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：闭包：如果在一个内部函数里，对在外部作用域(但不是在全局作用域）的变量进行引用，那么内部函数就被认为是 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：内嵌函数+高阶函数+闭包=》装饰器
预热两个范例:
范例一：函数参数固定
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')
范例二：函数参数不固定
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)-
无参装饰器
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. 有参装饰器
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：装饰器应用案例：
装饰器功能：函数超时则终止
# -*- coding: utf-8 -*-
from threading import Thread
import time
class TimeoutException(Exception):
pass
ThreadStop = Thread._Thread__stop#获取私有函数
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)
