How to write files in the background in Python? 

The idea is to use multi-threading in Python. It allows us to write files in the background while working on another operation. In this article, we will make a 'Asyncwrite.py' named file to demonstrate it. This program adds two numbers while it will also write a file in the background. Please run this program on your own system so that you can see the file made.

# Python3 program to write file in
# background

# Importing the threading and time 
# modules
import threading
import time

# Inheriting the base class 'Thread'
class AsyncWrite(threading.Thread): 

    def __init__(self, text, out):

        # calling superclass init
        threading.Thread.__init__(self) 
        self.text = text
        self.out = out

    def run(self):

        f = open(self.out, "a")
        f.write(self.text + '\n')
        f.close()

        # waiting for 2 seconds after writing
        # the file
        time.sleep(2)
        print("Finished background file write to",
                                         self.out)

def Main():
    
    message = "Geeksforgeeks"
    background = AsyncWrite(message, 'out.txt')
    background.start()
    
    print("The program can continue while it writes")
    print("in another thread")
    print("100 + 400 = ", 100 + 400)

    # wait till the background thread is done
    background.join() 
    print("Waited until thread was complete")

if __name__=='__main__':
    Main()

# Python3 program to write file in

# background

​

# Importing the threading and time 

# modules

import threading

import time

​

# Inheriting the base class 'Thread'

class AsyncWrite(threading.Thread): 

​

    def __init__(self, text, out):

​

        # calling superclass init

        threading.Thread.__init__(self) 

        self.text = text

        self.out = out

​

    def run(self):

​

        f = open(self.out, "a")

        f.write(self.text + '\n')

        f.close()

​

        # waiting for 2 seconds after writing

        # the file

        time.sleep(2)

        print("Finished background file write to",

                                         self.out)

​

def Main():

    message = "Geeksforgeeks"

    background = AsyncWrite(message, 'out.txt')

    background.start()

    print("The program can continue while it writes")

    print("in another thread")

    print("100 + 400 = ", 100 + 400)

​

    # wait till the background thread is done

    background.join() 

    print("Waited until thread was complete")

​

if __name__=='__main__':

    Main()

Output: 

Enter a string to store: HelloWorld
The program can continue while it writes in another thread
100 + 400 = 500
Finished background file write to out.txt
Waited until  thread was complete

The program will ask to enter a string and will calculate the sum of two numbers and in the background, it writes the 'entered string' to the output file named 'out.txt'.Check your directory where your 'Asyncwrite.py' file exists and you'll also find a file named 'out.txt' with your string stored in it.

Purpose:
The general purpose of writing files in the background is that you can add your data to a file in the background while making the program to do another task within the program. For eg. You can write the received input from the user to file while performing another task for the same user.

Reference:  

• Python3 basics
• Python3 intermediate level topics