PythonºÍSingleton £¨µ¥¼þ£©Ä£Ê½
ÎÒÖªµÀµÄÒ»ÖÖÔÚ
python
ÖÐ
Singleton mode
µÄʵÏÖÈçÏ£º
class Foo: pass
def
instance():
global inst
try:
inst
except:
inst =
Foo
()
return inst
¸ÃʵÏÖµÄÓŵã¾ÍÊǼòµ¥ºÍÖ±¹Û£¬µ«È±µãҲͬÑùÃ÷ÏÔ£º
ÐèÒª¿Í»§´úÂëÏÔʽ֪µÀÒ»¸ö½Ð
instance()
µÄ·½·¨À´´´½¨¸ÃÀàµÄ¶ÔÏó£»
ÔÚ²¢·¢»·¾³ÏÂÕâÖÖʵÏÖ²¢²»¿É¿¿£»
µÚ
2
µãÊÇÏ൱ÑÏÖصÄÒ»¸öȱÏÝ£¬Èç¹ûÄãÓÃÁËÉÏÃæµÄ´úÂ룬ÄÇÖ»ÄÜÆíµ»²»ÒªÓÐ
1
¸öÒÔÉϵÄʵÀý³öÏÖ£¨ËäÈ»¼¸Âʽϵͣ¬µ«»¹ÊÇÓпÉÄÜ£©£¬·ñÔò¾Í»á³öÏÖÏ¡Ææ¹Å¹ÖµÄÎÊÌâ¡£
Ò»¸öÉÔ΢ºÃЩʵÏÖÈçÏ£º
class
Singleton(object):
objs
= {}
def __new__(cls, *args, **kv):
if cls in cls.objs:
return cls.objs[cls]
cls.objs[cls] = object.__new__(cls)
Õâ¸öʵÏÖ½â¾öÁ˵ÚÒ»¸öȱµã£¬ÄÇЩֻÐèÒªÒ»¸öʵÀýµÄÀàÏëʵÏÖ
Singleton mode
£¬Ö»Òª´Ó
Singleton
Àà¼Ì³Ð¼´¿É£¬ÎÞÂÛÔÚ´úÂëµÄÄÄÀïʵÀý»¯¸ÃÀ࣬¶¼Ö»´æÔÚ¸ÃÀàµÄÒ»¸öʵÀý¡£
ΪÁ˽â¾öµÚ
2
¸öȱµã£¬Ò»¸ö½ø»¯µÄ°æ±¾³öÏÖÁË£¬ÈçÏ£º
class
Singleton(object):
objs
= {}
objs_locker =
threading.Lock()
def __new__(cls, *args, **kv):
if cls in cls.objs:
return cls.objs[cls]
cls.objs_locker.acquire()
try:
if cls in cls.objs: ## double check
locking
return cls.objs[cls]
&nb
Ïà¹ØÎĵµ£º
1. What’s the difference between all of the os.popen() methods?
popen2 doesn't capture standard error, popen3 does capture standard
error and gives a unique file handle for it. Finally, popen4 captures
standard error but includes it in the same file object as standard
output.
os.popen()&n ......
Python Áбí
listÊÇ´¦ÀíÒ»×éÓÐÐòÏîÄ¿µÄÊý¾Ý½á¹¹£¬¼´Äã¿ÉÒÔÔÚÒ»¸öÁбíÖд洢һ¸ö ÐòÁÐ µÄÏîÄ¿¡£¼ÙÏëÄãÓÐÒ»¸ö¹ºÎïÁÐ±í£¬ÉÏÃæ¼ÇÔØ×ÅÄãÒªÂòµÄ¶«Î÷£¬Äã¾ÍÈÝÒ×Àí½âÁбíÁË¡£Ö»²»¹ýÔÚÄãµÄ¹ºÎï±íÉÏ£¬¿ÉÄÜÿÑù¶«Î÷¶¼¶À×ÔÕ¼ÓÐÒ»ÐУ¬¶øÔÚPythonÖУ¬ÄãÔÚÿ¸öÏîÄ¿Ö®¼äÓöººÅ·Ö¸î¡£
ÁбíÖеÄÏîÄ¿Ó¦¸Ã°üÀ¨ÔÚ·½À¨ºÅÖУ¬ÕâÑùPython¾ÍÖªµÀÄãÊ ......
Python Ôª×é
Ôª×éºÍÁбíÊ®·ÖÀàËÆ£¬Ö»²»¹ýÔª×éºÍ×Ö·û´®Ò»ÑùÊÇ ²»¿É±äµÄ ¼´Äã²»ÄÜÐÞ¸ÄÔª×é¡£Ôª×éͨ¹ýÔ²À¨ºÅÖÐÓöººÅ·Ö¸îµÄÏîÄ¿¶¨Òå¡£Ôª×éͨ³£ÓÃÔÚʹÓï¾ä»òÓû§¶¨ÒåµÄº¯ÊýÄܹ»°²È«µØ²ÉÓÃÒ»×éÖµµÄʱºò£¬¼´±»Ê¹ÓõÄÔª×éµÄÖµ²»»á¸Ä±ä¡£
ʹÓÃÔª×é
Àý9.2 ʹÓÃÔª×é
#!/usr/bin/python
# Filename: using_tuple.py
zoo = ('wo ......
Ç°¼¸Ìì¿´µ½ÁËÒ»ÐÐÇó1000µÄ½×³ËµÄPython´úÂ룺
print
reduce
(
lambda
x
,
y
:
x
*
y
,
range
(
1
,
1001
))
Ò»ÏÂ×Ó±»python´úÂëµÄ¾«¼ò
Óë½ô´ÕËùÕÛ·þ£¬¹Ê¶Ô´úÂë½øÐÐÁ˼òµ¥µÄ·ÖÎö¡£
reduceÓërange¶¼ÊÇPythonµÄÄÚÖú¯Êý¡£
range£¨1£¬10 ......