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第一步：线程A修改了num的值为
7
第二步：线程C不知道num的值已经发生了改变，直接调用了num的值
7
第三步：线程B对num值加
1
，此时num值变为
8
第四步：线程B使用了num值
8
第五步：线程A使用了num值
8
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import
threading
import
time
number =
0
def run(num):
global number
number +=
1
print number
time.sleep(
1
)
for
i
in
range(
20
):
t = threading.Thread(target=run, args=(i,))
t.start()
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xpleaf@xpleaf-machine:/mnt/hgfs/Python/day6$ python thread_clock6.py
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import
threading
import
time
number =
0
lock = threading.RLock() #调用threading模块中的RLock()
def run(num):
lock.acquire() #开始给线程加锁
global number
number +=
1
lock.release() #给线程解锁
print number
time.sleep(
1
)
for
i
in
range(
20
):
t = threading.Thread(target=run, args=(i,))
t.start()
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xpleaf@xpleaf-machine:/mnt/hgfs/Python/day6$ python thread_clock6.py
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import
threading
import
time
number =
0
lock = threading.RLock()
def run(num):
lock.acquire()
global number
number +=
1
print number
time.sleep(
1
) #把time.sleep(
1
)也锁在线程中
lock.release()
for
i
in
range(
20
):
t = threading.Thread(target=run, args=(i,))
t.start()
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xpleaf@xpleaf-machine:/mnt/hgfs/Python/day6$ python thread_clock6.py
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xpleaf@xpleaf-machine:/mnt/hgfs/Python/day6$ time python thread_clock6.py | grep
'real'
real 0m20.073s
user 0m0.024s
sys 0m0.008s
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