Python threading, some printing messages turn concatenated in one line-CodePudding

Here I have a code containing a simple class printing something. I want to multithread it.

import threading
import time
import random


class Useless:
    def __init__(self, numb):
        self.numb = numb

    def printing(self):
        time.sleep(random.uniform(0.05, 0.09))
        print(f'number {self.numb} is being printed God knows what for...')

    def main_loop(self):
        for _ in range(5):
            self.printing()


obj_1 = Useless(1)
obj_2 = Useless(2)

proc_1 = threading.Thread(target=obj_1.main_loop, args=())
proc_2 = threading.Thread(target=obj_2.main_loop, args=())

proc_1.start()
proc_2.start()

The number of threads is arbitrary, so I can create more proc_. This is a key requirement!

But sometimes I receive a weird printing results like this:

number 2 is being printed God knows what for...number 1 is being printed God knows what for...

number 1 is being printed God knows what for...
number 2 is being printed God knows what for...
number 1 is being printed God knows what for...
number 2 is being printed God knows what for...
number 1 is being printed God knows what for...
number 2 is being printed God knows what for...
number 1 is being printed God knows what for...
number 2 is being printed God knows what for...

Process finished with exit code 0

You see sometimes some printed messages mix together and printed in one line but I would like them to be separate.

Probably subprocess pipe can help with it but I don't know how to implement it here. Probably Asyncio can solve it. So I want threads to be executed simultaneously (almost simultaneously within one core) but to have printed messages separated.

CodePudding user response：

Although there is no guarantees (this is highly OS specific), you can hardly send newline to stdout instead of python handling this

def printing(self):
    print(f'number {self.numb} is being printed God knows what for...\n', end='')

But I still do not recommend using this approach as it does not solve problem. Much appropriate way is to use some buffers and flush them synchronously

CodePudding user response：

just pass the flush keyword args into print function, and no print will be concatenated

print("Hello world", flush=True)