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Sharing and releasing issues of python class variables under multi-threading
Sharing and releasing issues of python class variables under multi-threading
I was tricked by multi-threading recently. I didn’t realize that class variables are shared under multi-threading. Another thing is that I didn’t realize the memory release problem, which made me more tired.
1. Python class variables in multi-threading situation The ones below are shared
2. The release of python class variables in multi-threaded situations is incomplete
3. The part of the memory that python class variables have not released in multi-threaded situations can be reused
import threading
import time
class Test:
cache = {}
@classmethod
def get_value(self, key):
value = Test.cache.get(key, [])
return len(value)
@classmethod
def store_value(self, key, value):
if not Test.cache.has_key(key):
Test.cache[key] = range(value)
else:
Test.cache[key].extend(range(value))
return len(Test.cache[key])
@classmethod
def release_value(self, key):
if Test.cache.has_key(key):
Test.cache.pop(key)
return True
@classmethod
def print_cache(self):
print 'print_cache:'
for key in Test.cache:
print 'key: %d, value:%d' % (key, len(Test.cache[key]))
def worker(number, value):
key = number % 5
print 'threading: %d, store_value: %d' % (number, Test.store_value(key, value))
time.sleep(10)
print 'threading: %d, release_value: %s' % (number, Test.release_value(key))
if __name__ == '__main__':
thread_num = 10
thread_pool = []
for i in range(thread_num):
th = threading.Thread(target=worker,args=[i, 1000000])
thread_pool.append(th)
thread_pool[i].start()
for thread in thread_pool:
threading.Thread.join(thread)
Test.print_cache()
time.sleep(10)
thread_pool = []
for i in range(thread_num):
th = threading.Thread(target=worker,args=[i, 100000])
thread_pool.append(th)
thread_pool[i].start()
for thread in thread_pool:
threading.Thread.join(thread)
Test.print_cache()
time.sleep(10)Public Unless the data is read-only, do not use it as class member variables. First, it will be shared, and second, it will be difficult to release.
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