Nrthugu

I trying to learn parallel programming and multiprocessing in python. I know that lock is like "sleep" so it make the other process waits until the current process finish that chunk of code or shared memory. But the problem is that the output is

import multiprocessing 

# function to withdraw from account 

def withdraw(balance, lock):     

    for _ in range(10): 

        lock.acquire() 

        print("with")

        balance.value = balance.value - 1

        lock.release() 

# function to deposit to account 

def deposit(balance, lock):     

    for _ in range(10): 

        lock.acquire()

        print("depp")

        balance.value = balance.value + 1

        lock.release() 



def perform_transactions(): 

    # initial balance (in shared memory) 

    balance = multiprocessing.Value('i', 100) 

    # creating a lock object 

    lock = multiprocessing.Lock() 

    # creating new processes 

    p1 = multiprocessing.Process(target=withdraw, args=(balance,lock)) 

    p2 = multiprocessing.Process(target=deposit, args=(balance,lock))   

    # starting processes 

    p1.start() 

    p2.start() 

    # wait until processes are finished 

    p1.join() 

    p2.join() 

    # print final balance 

    print("Final balance = {}".format(balance.value)) 

if __name__ == "__main__": 

    for _ in range(10):   

        # perform same transaction process 10 times 

        perform_transactions()       

first output:

with
with
with
with
with
with
with
with
with
with
depp
depp
depp
depp
depp
depp
depp
depp
depp
depp
Final balance = 100

I thought that it would be something like "dep with dep with ...etc" but it prints dep ten times and with 10 times which means it performed an entire process first with no parallelism.
It would make sense if the "lock.acquire()" was before the loop and "lock.release()" was after the loop.

Another output which is weird too

with

with

with

depp

depp

depp

depp

depp

depp

depp

depp

depp

depp

with

with

with

with

with

with

with

Final balance = 100