[英]How to stop multiprocessing in python running for the full script
我在python中有以下代碼:
import multiprocessing
import time
print "I want this to show once at the beggining"
def leaveout():
print "I dont Want This to Show"
def hang(input1):
print "I want this to show 3 times"
print "Number = %s" % input1
def main():
p = multiprocessing.Process(target=hang, args=("0"))
p.start()
p1 = multiprocessing.Process(target=hang, args=("1"))
p1.start()
p2 = multiprocessing.Process(target=hang, args=("2"))
p2.start()
p.join()
p1.join()
p2.join()
if __name__ == '__main__':
main()
print "I want this to show once at the end"
我的目標是在成功發生的三個實例中對hang函數進行多進程處理。 我的問題是,main函數還在以下輸出中重新運行了整個腳本的三個實例:
c:\Evopt>python multiprocessingprac.py
I want this to show once at the beggining
I want this to show once at the beggining
I want this to show once at the end
I want this to show 3 times
Number = 2
I want this to show once at the beggining
I want this to show once at the end
I want this to show 3 times
Number = 1
I want this to show once at the beggining
I want this to show once at the end
I want this to show 3 times
Number = 0
I want this to show once at the end
我該如何阻止這種情況發生?
生成新進程時,Windows將創建一個空白進程。 然后,在生成的過程中加載了一個新的Python解釋器,並為其提供了相同的代碼庫來進行解釋。
這就是為什么您看到重復的打印語句正在執行的原因。 由於它們是頂級表達式,因此每次過程將評估該代碼時都將執行它們。
在Unix OS中,這沒有被觀察到,因為它實現了完全不同的進程創建機制( fork
策略),該機制不需要在子進程中再次加載新的Python解釋器。
要解決您的問題,您需要從腳本中刪除print( ... )
表達式,並將其移至main
函數中。
def main():
print("I want this to show once at the beggining")
p0 = multiprocessing.Process( ... )
p0.start()
...
p2.join()
print("I want this to show once at the end")
您可以在多處理文檔中閱讀有關流程啟動策略的更多信息。
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