python Force git hook server side output on same line in realtime

Question

git hooks server side output only transmits on a newline. I want to configure a custom task and print real-time output on the same line. How can I achieve that? I tried sys.stdout.flush but it transmits everything once complete. It does work in real-time if I add a newline. I want something like

Step A)Started......Completed

with each '.' appended after a given time.

My current code looks like the following and it outputs only when the method is completed.

import sys, time, os


def print_realtime():
    sys.stdout.write('Started.')
    sys.stdout.flush()
    time.sleep(1)
    for i in range(1, 15):
        sys.stdout.write('.')
        sys.stdout.flush()
        time.sleep(0.5)

if __name__ == "__main__":
    print_realtime()

However, it works in realtime if I append '\n' like:

sys.stdout.write('.\n')

Welcome at Stackoverflow. Unfortunately I can't comprehend the nature of the problem. Please have a look at the SO guide on how to provide a [Minimal, Complete, and Verifiable example](https://stackoverflow.com/help/mcve). If you follow this guideline you will be much more likely getting useful answers. — MrLeeh, May 23 '17 at 07:54
That's still not a [mcve]. An MCVE would be a *complete Python program* that one could set up as a Git hook to demonstrate the problem. (Probably you should strip out all the ProcessPoolExecutor and logging code and just have a function that writes to stdout, unless that makes the problem go away, in which case you have a new clue.) — torek, May 23 '17 at 08:51
I added a python program which could be setup as git hook. If I execute the program directly it works fine appending '.' in real-time but when I set it up as pre-receive hook it just waits and prints everything at the end. Not sure what has to be changed. — Anamika Singh, May 23 '17 at 09:47

score 1 · Accepted Answer · answered May 23 '17 at 20:41

The problem comes down to the fact that Git itself does not print accumulated remote: text until the remote sends either a newline or carriage return.

Hence, if we change your inner loop to read:

for i in range(1, 15):
    sys.stdout.write('.' * i + '\r')
    sys.stdout.flush()
    time.sleep(0.5)

you will see the effect you desire.

Note that the \r moves the print position back to just after the word remote:, so we must repeat what we have printed so far (hence the need to print first one ., then two .s, then three, and so on).

python Force git hook server side output on same line in realtime

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