本文打算长期更新一些有意思的python代码片段，就当做是学习笔记。
1.python多线程死锁
import time,threading
locka = threading.Lock()
lockb = threading.Lock()
def fa():
print('a')
def fb():
print('b')
def fab():
locka.acquire()
try:
fa()
time.sleep(1)
lockb.acquire()
try:
fb()
finally:
lockb.release()
finally:
locka.release()
def fba():
lockb.acquire()
try:
fb()
time.sleep(1)
locka.acquire()
try:
fa()
finally:
locka.release()
finally:
lockb.release()
t1 = threading.Thread(target=fab)
t2 = threading.Thread(target=fba)
t1.start()
t2.start()
t1.join()
t2.join()
print('end')
locka = threading.Lock()
lockb = threading.Lock()
def fa():
print('a')
def fb():
print('b')
def fab():
locka.acquire()
try:
fa()
time.sleep(1)
lockb.acquire()
try:
fb()
finally:
lockb.release()
finally:
locka.release()
def fba():
lockb.acquire()
try:
fb()
time.sleep(1)
locka.acquire()
try:
fa()
finally:
locka.release()
finally:
lockb.release()
t1 = threading.Thread(target=fab)
t2 = threading.Thread(target=fba)
t1.start()
t2.start()
t1.join()
t2.join()
print('end')
2.协程coroutine(1)
来源：廖雪峰
def consumer():
r = ''
while True:
n = yield r
if not n:
return
print('[CONSUMER] Consuming %s...' % n)
r = '200 OK'
def produce(c):
c.send(None)
n = 0
while n < 5:
n = n + 1
print('[PRODUCER] Producing %s...' % n)
r = c.send(n)
print('[PRODUCER] Consumer return: %s' % r)
c.close()
c = consumer()
produce(c)
r = ''
while True:
n = yield r
if not n:
return
print('[CONSUMER] Consuming %s...' % n)
r = '200 OK'
def produce(c):
c.send(None)
n = 0
while n < 5:
n = n + 1
print('[PRODUCER] Producing %s...' % n)
r = c.send(n)
print('[PRODUCER] Consumer return: %s' % r)
c.close()
c = consumer()
produce(c)
运行结果为：
[PRODUCER] Producing 1...
[CONSUMER] Consuming 1...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 2...
[CONSUMER] Consuming 2...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 3...
[CONSUMER] Consuming 3...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 4...
[CONSUMER] Consuming 4...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 5...
[CONSUMER] Consuming 5...
[PRODUCER] Consumer return: 200 OK
[CONSUMER] Consuming 1...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 2...
[CONSUMER] Consuming 2...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 3...
[CONSUMER] Consuming 3...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 4...
[CONSUMER] Consuming 4...
[PRODUCER] Consumer return: 200 OK
[PRODUCER] Producing 5...
[CONSUMER] Consuming 5...
[PRODUCER] Consumer return: 200 OK
解释：
yield表达式本身没有返回值，它的返回值需要等到下次调用generator函数时，由send(args)函数的参数赋予。
3.协程coroutine(2)
来源：http://blog.csdn.net/gvfdbdf/article/details/49254037
# -*- 异步IO -*-
import asyncio
import threading
# @asyncio.coroutine把一个generator标记为coroutine类型
@asyncio.coroutine
def sub():
print('sub start: ...')
n = 10
while True:
print('yield start')
# asyncio.sleep()也是一个coroutine类型的generator，所以线程不会中断，而是直接执行下一个循环，等待yield from的返回
# 可以简单的理解为出现yield之后则开启一个协程(类似开启一个新线程),不管这个协程是否执行完毕，继续下一个循环
# 开启新协程后，print('yield start')会因为继续执行循环被立即执行，可以通过打印结果观察
r = yield from asyncio.sleep(1)
n = n - 1
print('---sub: %s, thread:%s' %(n, threading.currentThread()))
if n == 0:
break
@asyncio.coroutine
def add():
print('add start: ...')
n = 10
while True:
print('yield start')
r = yield from asyncio.sleep(2)
n = n + 1
print('+++add: %s, thread:%s' %(n, threading.currentThread()))
if n > 20:
break
# 获取EventLoop:
loop = asyncio.get_event_loop()
# 执行coroutine
tasks = [add(),sub()]
loop.run_until_complete(asyncio.wait(tasks))
loop.close()
import asyncio
import threading
# @asyncio.coroutine把一个generator标记为coroutine类型
@asyncio.coroutine
def sub():
print('sub start: ...')
n = 10
while True:
print('yield start')
# asyncio.sleep()也是一个coroutine类型的generator，所以线程不会中断，而是直接执行下一个循环，等待yield from的返回
# 可以简单的理解为出现yield之后则开启一个协程(类似开启一个新线程),不管这个协程是否执行完毕，继续下一个循环
# 开启新协程后，print('yield start')会因为继续执行循环被立即执行，可以通过打印结果观察
r = yield from asyncio.sleep(1)
n = n - 1
print('---sub: %s, thread:%s' %(n, threading.currentThread()))
if n == 0:
break
@asyncio.coroutine
def add():
print('add start: ...')
n = 10
while True:
print('yield start')
r = yield from asyncio.sleep(2)
n = n + 1
print('+++add: %s, thread:%s' %(n, threading.currentThread()))
if n > 20:
break
# 获取EventLoop:
loop = asyncio.get_event_loop()
# 执行coroutine
tasks = [add(),sub()]
loop.run_until_complete(asyncio.wait(tasks))
loop.close()
执行结果：
add start: ...
yield start add
sub start: ...
yield start sub
---sub: 9, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 11, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
---sub: 8, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
---sub: 7, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 12, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
---sub: 6, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
---sub: 5, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 13, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
---sub: 4, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
---sub: 3, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 14, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
......
yield start add
sub start: ...
yield start sub
---sub: 9, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 11, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
---sub: 8, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
---sub: 7, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 12, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
---sub: 6, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
---sub: 5, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 13, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
---sub: 4, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
---sub: 3, thread:<_MainThread(MainThread, started 140735116865536)>
yield start sub
+++add: 14, thread:<_MainThread(MainThread, started 140735116865536)>
yield start add
......