파이썬의 스레드(thread)2

"프로그래밍 언어의 개념과 흐름에 대한 고찰 - 파이썬답게 코딩하기" 학습중...

동시성과 관련한 thread 기법에 대해 어렴풋이 알거나 몰랐던 내용들 몇가지 정리해봅니다.

Thread Event

# ## Thread Event
# import time
# import logging
# import threading
#
# logging.basicConfig(level = logging.DEBUG, format = "(%(threadName)s) %(message)s")
#
# # >>> e = threading.Event()
# # >>> e.isSet()
# # False
# # >>> e.set()
# # >>> e.isSet()
# # True
# # >>> e.clear()
# # >>> e.isSet()
# # False
#
# def first_wait(e1, e2) :
#     while not e1.isSet() :
#         event = e1.wait(1)
#         logging.debug("Event Status : (%s)", event) ## logging에서 message 출력 부분
#
#         if event :
#             logging.debug("e1 is set.")
#             time.sleep(3)
#             logging.debug("Set e2")
#             e2.set()
#
# def second_wait(e2) :
#     while not e2.isSet() :
#         event = e2.wait(1)
#         logging.debug("Event Status : (%s)", event) ## logging에서 message 출력 부분
#
#         if event :
#             logging.debug("e2 is set.")
#
# def main() :
#     e1 = threading.Event()
#     e2 = threading.Event()
#
#     t1 = threading.Thread(name = 'first', target = first_wait, args = (e1, e2)) ## logging에서 threadName = name = first
#     t1.start()
#
#     t2 = threading.Thread(name = 'second', target = second_wait, args = (e2,))
#     t2.start()
#
#     logging.debug("wait...")
#     time.sleep(5)
#     logging.debug("Set e1")
#     e1.set()
#     time.sleep(5)
#     logging.debug("exit")
#
# if __name__ =="__main__" :
#     main()

# (MainThread) wait...
# (second) Event Status : (False)
# (first) Event Status : (False)
# (first) Event Status : (False)
# (second) Event Status : (False)
# (second) Event Status : (False)
# (first) Event Status : (False)
# (second) Event Status : (False)
# (first) Event Status : (False)
# (MainThread) Set e1
# (first) Event Status : (True)
# (first) e1 is set.
# (second) Event Status : (False)
# (second) Event Status : (False)
# (second) Event Status : (False)
# (first) Set e2
# (second) Event Status : (True)
# (second) e2 is set.
# (MainThread) exit

Thread Lock

## Thread Lock

# import time
# import logging
# import threading
# 
# logging.basicConfig(level = logging.DEBUG, format = "(%(threadName)s) %(message)s")
# 
# def blocking_lock(lock) :
#     logging.debug("start blocking lock")
# 
#     while True :
#         time.sleep(1)
#         lock.acquire() ## .acquire() 메서드가 lock을 잡기 위한 메서드인데 아무런 인자값을 주지 않으면 잡을 때까지 block됨.
#         try :
#             logging.debug("grab it")
#             time.sleep(0.5)
#         finally :
#             logging.debug("release")
#             lock.release()
# 
# # python threading 패키지에서는 Lock을 지원한다.
# # lock을 acquire하면 해당 쓰레드만 공유 데이터에 접근할 수 있고,
# # lock을 release 해야 다른 쓰레드에서 공유 데이터에 접근할 수 있다.
# 
# def nonblocking_lock(lock) :
#     logging.debug("start nonblocking lock")
#     attempt = 0
#     grab = 0
#     while grab < 3 :
#         time.sleep(1)
#         logging.debug("attempt")
#         success = lock.acquire(False) ## acquire 인자로 False를 전달하여 이 쓰레드는 block되지 않고 다음 로직을 수행.
#         try :
#             attempt += 1
#             if success : ## acquire를 하게 되면 True를 반환하여 이하 구문을 실행.
#                 logging.debug("grab it")
#                 grab += 1
#         finally :
#             if success :
#                 logging.debug("release")
#                 lock.release()
# 
#     logging.debug("attempt : %s, grab : %s" % (attempt, grab))
# 
# def main():
#     lock = threading.Lock()
#     blocking = threading.Thread(target = blocking_lock, name = "blocking", args = (lock,))
#     blocking.setDaemon(True)
#     blocking.start()
# 
#     nonblocking = threading.Thread(target = nonblocking_lock, name = "nonblocking", args = (lock,))
#     nonblocking.start()
# 
# if __name__ == "__main__" :
#     main()
# 
# # (blocking) start blocking lock
# # (nonblocking) start nonblocking lock
# # (nonblocking) attempt
# # (blocking) grab it
# # (blocking) release
# # (nonblocking) attempt
# # (nonblocking) grab it
# # (nonblocking) release
# # (blocking) grab it
# # (nonblocking) attempt
# # (blocking) release
# # (nonblocking) attempt
# # (nonblocking) grab it
# # (nonblocking) release
# # (blocking) grab it
# # (blocking) release
# # (nonblocking) attempt
# # (nonblocking) grab it
# # (nonblocking) release
# # (nonblocking) attempt : 5, grab : 3