I am using Ubuntu 20.04 so my system version of Python is 3.8.5. I have installed Python 3.9.1 using pyenv and have set up a folder-specific python as follows:
$ pyenv local 3.9.1
$ cat .python-version
3.9.1
Pyenv's shims are present and available in $PATH:
$ which python
/home/username/.pyenv/shims/python
$ which python3
/home/username/.pyenv/shims/python3
Pyenv itself correctly recognises the version that I want to use:
$ pyenv which python
/home/username/.pyenv/versions/3.9.1/bin/python
$ pyenv which python3
/home/username/.pyenv/versions/3.9.1/bin/python3
However, when I run python or python3, only the former gives me the correct version, while python3 reverts to the system version:
$ python --version
Python 3.9.1
$ python3 --version
Python 3.8.5
What could be the problem? I installed pyenv using its own installer (the script at https://pyenv.run) and my .bashrc contains the following lines as per the instructions:
export PATH="/home/username/.pyenv/bin:$PATH"
eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"