how to write to file in multiprocess in python

Question

I want to write a process id to file whenever start my program, so I wrote this code, but this code write pid to file whenever stop the process.

from multiprocessing import Process
from os import getpid


def f():
    file = open('udp.pid', 'w')
    file.write(str(getpid()))
    file.close()
    while True:
        # a socket infinity loop
        pass

if __name__ == '__main__':
    p = Process(target=f,)
    p.start()

how to write pid to file in multiprocess?

UPDATE:

I use python 3.4 on windows 8.1

han058 · Accepted Answer · 2015-06-23 05:21:09Z

1

I think using multiprocess or not does not matter. It just about write!

open(name[, mode[, buffering]])

in https://docs.python.org/2/library/functions.html

The optional buffering argument specifies the file’s desired buffer size: 0 means unbuffered, 1 means line buffered, any other positive value means use a buffer of (approximately) that size (in bytes).

change your code

file = open('udp.pid', 'w')

to

file = open('udp.pid', 'wb', 0)

edited Jun 23, 2015 at 5:21

answered Jun 23, 2015 at 5:15

han058

9088 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Foad Tahmasebi Over a year ago

I tested it and got this error "ValueError: can't have unbuffered text I/O"

Foad Tahmasebi Over a year ago

nothing happened !, I use python-3.4, I change 'w' to 'wb', and "file.write(str(getpid()))" to "file.write(str(getpid()).encode('utf-8))" but nothing changed, the program write pid to file after end process!

han058 Over a year ago

I tested the code on OS X. It works! Event your code wrote pid immediatley what you expected.

han058 Over a year ago

Please refer to this page, stackoverflow.com/questions/18194374/…

user707650 Over a year ago

Why use binary mode when writing a simple string?

|

Collectives™ on Stack Overflow

how to write to file in multiprocess in python

1 Answer 1

8 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related