python threading模块有两类锁：互斥锁（threading.Lock ）和可重用锁（threading.RLock）。两者的用法基本相同，具体如下：
lock = threading.Lock()
lock.acquire()
dosomething……
lock.release()
RLock的用法是将threading.Lock()修改为threading.RLock()。便于理解，先来段代码：
[root@361way lock]# cat lock1.py
#!/usr/bin/env python
# coding=utf-8
import threading # 导入threading模块
import time # 导入time模块
class mythread(threading.Thread): # 通过继承创建类
def __init__(self,threadname): # 初始化方法
# 调用父类的初始化方法
threading.Thread.__init__(self,name = threadname)
def run(self): # 重载run方法
global x # 使用global表明x为全局变量
for i in range(3):
x = x + 1
time.sleep(5) # 调用sleep函数，让线程休眠5秒
print x
tl = [] # 定义列表
for i in range(10):
t = mythread(str(i)) # 类实例化
tl.append(t) # 将类对象添加到列表中
x=0 # 将x赋值为0
for i in tl:
i.start()
这里执行的结果和想想的不同，结果如下：
[root@361way lock]# python lock1.py
30
30
30
30
30
30
30
30
30
30
为什么结果都是30呢？关键在于global 行和 time.sleep行。
1、由于x是一个全局变量，所以每次循环后 x 的值都是执行后的结果值；
2、由于该代码是多线程的操作，所以在sleep 等待的时候，之前已经执行完成的线程会在这等待，而后续的进程在等待的5秒这段时间也执行完成 ，等待print。同样由于global 的原理，x被重新斌值。所以打印出的结果全是30 ；
3、便于理解，可以尝试将sleep等注释，你再看下结果，就会发现有不同。
在实际应用中，如抓取程序等，也会出现类似于sleep等待的情况。在前后调用有顺序或打印有输出的时候，就会现并发竞争，造成结果或输出紊乱。这里就引入了锁的概念，上面的代码修改下，如下：
[root@361way lock]# cat lock2.py
#!/usr/bin/env python
# coding=utf-8
import threading # 导入threading模块
import time # 导入time模块
class mythread(threading.Thread): # 通过继承创建类
def __init__(self,threadname): # 初始化方法
threading.Thread.__init__(self,name = threadname)
def run(self): # 重载run方法
global x # 使用global表明x为全局变量
lock.acquire() # 调用lock的acquire方法
for i in range(3):
x = x + 1
time.sleep(5) # 调用sleep函数，让线程休眠5秒
print x
lock.release() # 调用lock的release方法
lock = threading.Lock() # 类实例化
tl = [] # 定义列表
for i in range(10):
t = mythread(str(i)) # 类实例化
tl.append(t) # 将类对象添加到列表中
x=0 # 将x赋值为0
for i in tl:
i.start() # 依次运行线程
执行的结果如下：
[root@361way lock]# python lock2.py
3
6
9
12
15
18
21
24
27
30
加锁的结果会造成阻塞，而且会造成开锁大。会根据顺序由并发的多线程按顺序输出，如果后面的线程执行过快，需要等待前面的进程结束后其才能结束 －－－ 写的貌似有点像队列的概念了 ，不过在加锁的很多场景下确实可以通过队列去解决。
最后，再引入一个示例，在股票量化分析（二）PE和流通市值篇中，介绍了如何采集stock的两个指标，并按结果输出，不过在输出的时候发有会出现输出紊乱，如下：
如600131和000708的stockid就输出到了同一行，虽然通过多线程使执行速度快了很多 ，但这样很不美观，也不便于后续处理。
1、输出竞争紊乱代码
#!/usr/bin/python
#coding=utf-8
# 1、pe在 0~20 之间的企业
# 2、流通股本小于50亿的企业
import urllib2
import time
import json
from threading import Thread
def get_pe(stockid):
try:
url = 'http://d.10jqka.com.cn/v2/realhead/hs_%s/last.js' % stockid
send_headers = {
'Host':'d.10jqka.com.cn',
'Referer':'http://stock.10jqka.com.cn/',
'Accept':'application/json, text/javascript, */*; q=0.01',
'Connection':'keep-alive',
'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36',
'X-Forwarded-For':'124.160.148.178',
'X-Requested-With':'XMLHttpRequest'
}
req = urllib2.Request(url,headers=send_headers)
f = urllib2.urlopen(req)
data = f.read().split('items":',1)[1]
data = data.split('})',1)[0]
J_data = json.loads(data)
#J_data = json.dumps(data,indent=4,encoding='utf-8')
stockpe = J_data['2034120']
stockname = J_data['name']
sumvalue = J_data['3475914']
currentprice = J_data['10']
#print stockid,stockname,stockpe
return stockname,stockpe,sumvalue,currentprice
except urllib2.HTTPError, e:
#return stockid ,'get happed httperror'
return e.code
def cond(stockid,pe,asset):
pe = int(pe)
asset = int(asset)
try:
stockname,stockpe,sumvalue,currentprice = get_pe(stockid)
if sumvalue:
Billvalue = round(float(sumvalue)/1000/1000/100)
else:
Billvalue = 0
if stockpe:
if float(stockpe) > 0 and float(stockpe) < pe and Billvalue < asset :
print stockid,stockname,currentprice,stockpe,Billvalue
#else:
# print stockid
except TypeError ,e:
print stockid ,'get is error'
if __name__ == '__main__':
threads = []
print 'stockid stockname currentprice stockpe Billvalue'
stockids = [line.strip() for line in open("stock_exp.txt", 'r')]
nloops = range(len(stockids))
for stockid in stockids:
t = Thread(target=cond, args=(stockid,28,80))
threads.append(t)
for i in nloops:
threads[i].start()
for i in nloops:
threads[i].join()
2、加锁后的代码
#!/usr/bin/python
#coding=utf-8
# 1、pe在 0~20 之间的企业
# 2、流通股本小于50亿的企业
import threading
import urllib2
import time
import json
lock = threading.Lock()
def get_pe(stockid):
try:
url = 'http://d.10jqka.com.cn/v2/realhead/hs_%s/last.js' % stockid
send_headers = {
'Host':'d.10jqka.com.cn',
'Referer':'http://stock.10jqka.com.cn/',
'Accept':'application/json, text/javascript, */*; q=0.01',
'Connection':'keep-alive',
'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 Safari/537.36',
'X-Forwarded-For':'124.160.148.178',
'X-Requested-With':'XMLHttpRequest'
}
req = urllib2.Request(url,headers=send_headers)
f = urllib2.urlopen(req)
data = f.read().split('items":',1)[1]
data = data.split('})',1)[0]
J_data = json.loads(data)
#J_data = json.dumps(data,indent=4,encoding='utf-8')
stockpe = J_data['2034120']
stockname = J_data['name']
sumvalue = J_data['3475914']
currentprice = J_data['10']
#print stockid,stockname,stockpe
return stockname,stockpe,sumvalue,currentprice
except urllib2.HTTPError, e:
#return stockid ,'get happed httperror'
return e.code
def cond(stockid,pe,asset):
pe = int(pe)
asset = int(asset)
try:
stockname,stockpe,sumvalue,currentprice = get_pe(stockid)
if sumvalue:
Billvalue = round(float(sumvalue)/1000/1000/100)
else:
Billvalue = 0
if stockpe:
if float(stockpe) > 0 and float(stockpe) < pe and Billvalue < asset :
lock.acquire()
print stockid,stockname,currentprice,stockpe,Billvalue
lock.release()
#else:
# print stockid
except TypeError ,e:
print stockid ,'get is error'
if __name__ == '__main__':
threads = []
print 'stockid stockname currentprice stockpe Billvalue'
stockids = [line.strip() for line in open("stock_exp.txt", 'r')]
for stockid in stockids:
t = threading.Thread(target=cond, args=(stockid,25,50))
threads.append(t)
t.start()