Proses Multiproses Tidak Dapat Berbagi Variabel Global | Panduan Memulai Python Bagian 106

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Proses Multiproses Tidak Dapat Berbagi Variabel Global | Panduan Memulai Python Bagian 106

Proses Multiproses Tidak Dapat Berbagi Variabel Global. Dua thread anak dalam proses utama yang sama. Thread dapat berbagi variabel global dari proses yang sama, sedangkan proses yang berbeda masing-masing menyimpan variabel global dan tidak berbagi variabel global.
Beberapa proses tidak dapat berbagi variabel global
import os , multiprocessing, threading

n = 100


def test () :
global n
n += 1
print( The value of n in 'test===={} is {}' .format( os.getpid (), hex(id(n))))


def demo () :
global n
n += 1
print( The value of n in 'demo===={} is {}' .format( os.getpid (), hex(id(n))))


print( threading.current_thread ().name)
test() # 101
demo() # 102

# Two child threads in the same main process. Threads can share global variables of the same process

# t1 = threading.Thread (target=test)
# t2 = threading.Thread (target=demo)
# t1.start()
# t2.start()

# if __name__ == '__main__':
# Each process saves a global variable and does not share global variables
# p1 = multiprocessing.Process (target=test)
# p2 = multiprocessing.Process (target=demo)
# p1.start() # 101
# p2.start() # 101
Contoh:
from multiprocessing import Process
import os

nums = [ 11 , 22 ]

def work1 () :
"""The code to be executed by the child process"""
print( "in process1 pid =%d , nums =%s" %( os.getpid (), nums ))
for i in range( 3 ):
nums.append ( i )
print( "in process1 pid =%d , nums =%s" %( os.getpid (), nums ))

def work2 () :
"""The code to be executed by the child process"""
nums.pop ()
print( "in process2 pid =%d , nums =%s" %( os.getpid (), nums ))

if __name__ == '__main__':
p1 = Process(target=work1)
p1.start()
p1.join()

p2 = Process(target=work2)
p2.start()

print('in process0 pid={} ,nums={}'.format(os.getpid(),nums))
Hasil eksekusi:
in process1 pid=2707 ,nums=[11, 22]
in process1 pid=2707 ,nums=[11, 22, 0]
in process1 pid=2707 ,nums=[11, 22, 0, 1]
in process1 pid=2707 ,nums=[11, 22, 0, 1, 2]
in process0 pid=2706 ,nums=[11, 22]
in process2 pid=2708 ,nums=[11]