How to solve UnicodeDecodeError in Python 3.6?

I had this issue when using Python inside a Docker container based on Ubuntu 18.04. It appeared to be a locale issue, which was solved by adding the following to the Dockerfile:

ENV LANG C.UTF-8

It sounds like your locale is broken and have another bytes->Unicode issue. The thing you did for Python 2.7 is a hack that only masked the real problem (there's a reason why you have to reload sys to make it work).

To fix your locale, try typing locale from the command line. It should look something like:

LANG=en_GB.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_GB.UTF-8"
LC_TIME="en_GB.UTF-8"
LC_COLLATE="en_GB.UTF-8"
LC_MONETARY="en_GB.UTF-8"
LC_MESSAGES="en_GB.UTF-8"
LC_ALL=

locale depends on LANG being set properly. Python effectively uses locale to work out what encoding to use when writing to stdout in. If it can't work it out, it defaults to ASCII.

You should first attempt to fix your locale. If locale errors, make sure you've installed the correct language pack for your region.

If all else fails, you can always fix Python by setting PYTHONIOENCODING=UTF-8. This should be used as a last resort as you'll be masking problems once again.

If Python is still throwing an error after setting PYTHONIOENCODING then please update your question with the stacktrace. Chances are you've got an implied conversion going on.