print(c, end="") doesn't seem to work consistently across Python versions on Windows?

[JasonMendoza2008]

Bug report

Bug description:

Define a class like so:

class C:
    def __init__(self):
        pass
    def __str__(self):
        return "C"

Instantiate it c = C() and do print(c, end="").

On Python 3.14.1 (tags/v3.14.1:57e0d17, Dec 2 2025, 14:05:07) [MSC v.1944 64 bit (AMD64)] on win32, nothing gets printed (but print(c) works):

On Python 3.12.5 (tags/v3.12.5:ff3bc82, Aug 6 2024, 20:45:27) [MSC v.1940 64 bit (AMD64)] on win32 everything seems fine and works as I would've expected:

Maybe it's not a bug and I'm just stupid? Sorry if that's the case..

Operating systems tested on:

Windows

Note

I'm not using any IDE, I'm just double clicking on the corresponding python.exe. Yes my 3.12 is outdated, but it has the "correct" behaviour.

[XChaitanyaX]

works fine in all versions when executed via a file like python file.py in cmd.
probably a REPL issue.

[gvanrossum]

Smells like a buffer gets lost. Probably adding flush=True will work around it.

Do you need the helper class? Or does it work the same way when you just do `print("C", end="")?

Can't repro right now, not a Windows machine in sight. :-)

[JasonMendoza2008]

Smells like a buffer gets lost. Probably adding flush=True will work around it.

Do you need the helper class? Or does it work the same way when you just do `print("C", end="")?

Can't repro right now, not a Windows machine in sight. :-)

Yeah, turns out my MRE was not at all minimal. Flushing doesn't do much.

[sergey-miryanov]

It is known bug with PyREPL #128067