BrokenPipeError when writing to sys.stdout and a Linux pipe

Asked Aug 07 '22 at 01:04

Active Aug 07 '22 at 05:55

Viewed 128 times

I want to write to sys.stdout in a way that the output can be 'piped' in Linux (e.g. with | head). I thought I was being clever with the following code: by specifying sys.stdout as the file, I can let my program write to STDOUT or a file depending on the input flag.

def write(outfile: str, data: str):
    try:
        fp = sys.stdout  # already an open descriptor
        if outfile:  # user wants to write to file
            fp = open(outfile, "w+")
            
        fp.write(data)
    except Exception as e:
        print("Could not write to file", e)

This works fine. However, when I decide to run the command with a pipe:

python3 command.py | head

I get a BrokenPipeError. Why is this?

edited Aug 07 '22 at 05:55

asked Aug 07 '22 at 01:04

bluppfisk

2,538
3
27
56

How many lines of output is your program trying to write? – Joseph Sible-Reinstate Monica Aug 07 '22 at 03:04
It's trying to write 13001 lines :) It writes them just fine to the terminal if I'm not using `| head` – bluppfisk Aug 07 '22 at 05:55
1

Does this answer your question? [How to prevent BrokenPipeError when doing a flush in Python?](https://stackoverflow.com/questions/26692284/how-to-prevent-brokenpipeerror-when-doing-a-flush-in-python) – Joseph Sible-Reinstate Monica Aug 07 '22 at 06:07
1

See also https://docs.python.org/3/library/signal.html#note-on-sigpipe – Joseph Sible-Reinstate Monica Aug 07 '22 at 06:08

BrokenPipeError when writing to sys.stdout and a Linux pipe

0 Answers0