Python 2.7 inside Docker cannot print unicode without --tty

[hyperknot]

I'm trying to run a simple Python app in Docker, using the official python:2.7 image.

My problem is that unless I enable -t / --tty in docker run, the python print command terminates when trying to print Unicode characters:

UnicodeEncodeError: 'ascii' codec can't encode characters...

If I enable --tty it works without errors.

The problem is that I want to run this process in the background, using --detach and that mode does not support --tty.

What kind of changes do I need to make to my Dockerfile so that it doesn't terminate when trying to print Unicode strings?

Minimal Dockerfile:

FROM python:2.7

CMD [ "python", "-c", "print (u'\\xc1')" ]

Minimal broken run command:

# error
docker run myimage 

# working
docker run --tty myimage

Note: it also works without problems in the official python:3.5 image.

[yosifkit]

You can run a container with -d and -t.

docker run -dt --name python python:2 python -c 'print (u"\xc1")'
a191fc9b251aa25e078d3537b6bd4a3e1928d39a0cb0104c4a661a9da067e242
$ docker logs python
Á

[hyperknot]

@yosifkit it wasn't working for me.

Anyway, I found the real fix. It is to set:

ENV PYTHONIOENCODING UTF-8

It might be a good idea to add this to the 2.7 Docker file, but at least anyone can add it to their own Dockerfile. Hopefully this ticket can be found by Google.

[tianon]

Given that we explicitly set ENV LANG C.UTF-8 (http://bugs.python.org/issue19846), I'm +1 on adding ENV PYTHONIOENCODING UTF-8 for Python 2. 👍

[xsteadfastx]

👍 i always run into that problem and need to google around what environment varible i should add to fix it.

[tianon]

Finally made a PR: #278