CODEWITHSUNDEEP
pythonpython-3.xmultiprocessing
Kobe Janssens
Kobe Janssens

Reputation: 318

How to access global variables when making use of multiproccesing in python?

I'm making use of different processes but I'm unable to make use of global variable. I have 2 processes, 1 how gather data from an api and the last process uses this data and does some calculations on the obtained data. I've followed this article but it doesn't work for me. Can someone help me?

import pandas as pd
import numpy as np
import multiprocessing
import time

class Example():
    def __init__(self):
        manager = multiprocessing.Manager()

        self.curValues1 = manager.dict()

    def main(self):
        p1 = multiprocessing.Process(target=self.gatherProcess1)
        p2 = multiprocessing.Process(target=self.calc)
        p1.start()
        p2.start()
        p1.join()
        p2.join()

    def gatherProcess1(self):
        df = pd.DataFrame([['tom', 10], ['nick', 15], ['juli', 14]], columns = ['Name', 'Age'])  # Get data from api

        self.curValues1 = {"lastName": df["Name"].iloc[-1], "lastAge": df["Age"].iloc[-1]}

    def calc(self):
        time.sleep(1)
        print(self.curValues1["lastName"], self.curValues1["lastAge"])

example = Example()

example.main()

Upvotes: 0

Views: 43

Answers (1)

dano
dano

Reputation: 94881

You have to update self.curValues1 dict in place, not re-assign it:

self.curvalues1.update({"lastName": df["Name"].iloc[-1], "lastAge": df["Age"].iloc[-1]})

When you re-assign self.curValues1 the way you currently do, you just throw away the multiprocessing.Manager dict and assign it to a regular dict.

Upvotes: 2

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