python學習七：正則表達式、多線程初探

原創

2020-02-21 17:04

1. 正則表達式

import re

content = """Python was created in the early 1990s by Guido van Rossum at Stichting Mathematisch Centrum (CWI, see http://www.cwi.nl) in the Netherlands as a successor of a language called ABC.  Guido remains Python's principal author, although it includes many contributions from others."""

# re module function: compile
# re module / regex object functins: match, search, findall, finditer, 
# matching object functins: split, sub, group, groups

print "RE learning"
print "1."
m = re.match("Python", content)  # return match obj
if m is not None:
	print type(m.group())
	print m.group()				# get a string

m = re.search(r"\bthe\b", content)
if m is not None:
	print type(m.group())
	print m.group()

print "2."
m = re.match('(\w\w\w)-(\d\d\d)', 'abc-123')
print m.group()		
print m.group(1)		# get the first s ubgroup string
print m.group(2)
print m.groups()		# get the strings in a tuple

print "3."
m = re.search('^The', 'The end.')
if m is not None: print m.group()

m = re.search(r'\bthe', 'in the room')
if m is not None: print m.group()

m = re.findall(r'\bthe\b', content)	# return a list of string
if m is not None: print m 			

print "4."
m = re.sub('X', 'Mr. Zhang', 'to: X\nDear X\n')  # return a string
print m

m = re.subn('X', 'Mr. Zhang', 'to: X\nDear X\n') # return a tuple
print m

print "5."
m = re.split(':', 'str1:str2:str3') # return a list, and can use RE as delimiter
print m

2. 多線程
python虛擬機的訪問由全局解釋器鎖（GIL）來控制，保證同一時刻只有一個線程在運行。
流程：1. 設置GIL 2. 運行線程 3. 運行指定數量的指令或者主動讓出控制（例如time.sleep(0)） 4. 設置線程爲休眠狀態 5. 解鎖GIL
在調用外部代碼（如C/C++擴展函數）的時候，GIL將會被鎖定，直到這個函數結束爲止。
不使用thread模塊的考慮：
（1） threading跟完善
（2） threading模塊有豐富的同步原語
（3）對進程什麼時候結束完全沒有控制，threading模塊可以確保重要的子線程退出後進程才退出。

print "Thread learning"
print "a running function"
import threading
from time import sleep, ctime

loops = [4,2]

def loop(nloop, nsec):
	print "start loop", nloop, "at time:", ctime()
	sleep(nsec)
	print "loop", nloop, "Done at time:", ctime()

def main():
	print "main starting at:", ctime()
	threads = []
	nloops = range(len(loops))

	for i in nloops:
		t = threading.Thread(target = loop, args = (i, loops[i]))
		threads.append(t)

	for i in nloops:
		threads[i].start()

	for i in nloops:
		threads[i].join()

	print "all Done at time:", ctime()

#if __name__ == '__main__':
#	main()

print "an class object"

class ThreadFunc(object):
	def __init__(self, func, args, name=''):
		self.name = name
		self.func = func
		self.args = args

	def __call__(self):
		apply(self.func, self.args)

def main2():
	# t = threading.Thread(target = ThreadFunc(loop, (i, loops[i]), loop.__name__))