python based Dockerfile throws locale.Error: unsupported locale setting

Question

I have a problem with passing the host's (Centos7) locales to the python3 docker image. Only the following locales end up in the image, even though I used the suggestion described in the link below:

C
C.UTF-8
POSIX

Why does locale.getpreferredencoding() return 'ANSI_X3.4-1968' instead of 'UTF-8'?

My Dockerfile has:

FROM python:3.7.5
ENV LC_ALL C.UTF-8
WORKDIR /data
ADD ./requirements.txt /data/requirements.txt
RUN pip install -r requirements.txt
COPY . /data
CMD [ "python3", "./test.py" ]

When I run this command:

locale.setlocale(locale.LC_ALL,'ru_RU')

it throws this error:

Traceback (most recent call last):
      File "./test.py", line 10, in <module>
        locale.setlocale(locale.LC_ALL,'ru_RU')
      File "/usr/local/lib/python3.7/locale.py", line 608, in setlocale
        return _setlocale(category, locale)
    locale.Error: unsupported locale setting

If I set

ENV LANG ru_RU.UTF-8
ENV LC_ALL ru_RU.UTF-8

Then I get:

locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_COLLATE to default locale: No such file or directory
locale.getdefaultlocale ('ru_RU', 'UTF-8')
locale.getpreferredencoding UTF-8
Exception: unsupported locale setting

Please, explain how can I add a ru_RU locale into the python image?

kendriu · Accepted Answer · 2020-01-08 15:09:38Z

28

What I would do for Debian based docker image:

FROM python:3.7.5

RUN apt-get update && \
    apt-get install -y locales && \
    sed -i -e 's/# ru_RU.UTF-8 UTF-8/ru_RU.UTF-8 UTF-8/' /etc/locale.gen && \
    dpkg-reconfigure --frontend=noninteractive locales

ENV LANG ru_RU.UTF-8
ENV LC_ALL ru_RU.UTF-8

and then in python:

import locale

locale.setlocale(locale.LC_ALL,'ru_RU.UTF-8')

edited Jan 8, 2020 at 15:09

answered Jan 7, 2020 at 22:57

kendriu

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8 Comments

khassen Over a year ago

Thank you. You meant yum install -y locales since I have Centos. Are you sure if it is possible to call yum in python based image? I have FROM python, but not FROM centos.

kendriu Over a year ago

It is not a problem. After all, it is still a Linux distro.

kendriu Over a year ago

I've tested my solution with Debian-based image. Let me know if it works for Centos

kendriu Over a year ago

From the dockerfile that you posted, it looks like you are using this image hub.docker.com/layers/python/library/python/3.7.5/images/… which seems to be Debian-based. If that's true, my Dockerfile is correct and does not need extra edit

kendriu Over a year ago

In other words apt-get, not yum :)

|

seanick · Accepted Answer · 2022-05-18 02:39:34Z

1

For anyone who can't get the accepted answer to work with intended locales such as en_IN.UTF-8, be wary of spaces in your locale in /etc/locale.gen.

try this:

FROM python:3.8

RUN apt-get update && \
    apt-get install -y locales && \
    sed -i -e 's/# en_IN UTF-8/en_IN UTF-8/' /etc/locale.gen && \
    dpkg-reconfigure --frontend=noninteractive locales

ENV LANG en_IN.UTF-8
ENV LC_NUMERIC en_IN.UTF-8

After dpkg-reconfigure, the locale should be available as en_IN.UTF-8

answered May 18, 2022 at 2:39

seanick

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