Develop Reference

pip install "moduleNotFound" error in .venv after Installing / upgrading-to Python 3.11 on macOS with pyenv

I use pyenv (installed with homebrew) to manage my macOS python-versions.
Python 3.11 just came out, but pyenv doesn't see this version. However from googling it appears others are able to see/install it.
How to fix?
This caused me some trouble, so I'm gona jot my solution down in case it's useful (and in case others can improve upon the solution path).
EDIT: On a fresh macOS, I bumped into: UserWarning: Could not import the lzma module. Your installed Python is incomplete and (as per answers there) did brew install xz before pyenv install 3.11.0.
The first issue was that the homebrew-installed pyenv doesn't see the new 3.11. So I had to uninstall it and re-install using pyenv's recommended method:
> brew uninstall pyenv
> # rm -rf ~/.pyenv
> curl https://pyenv.run | bash
> pyenv install 3.11.0
> pyenv global 3.11.0
> which python ; python --version # sanity check
(Note: You'll lose your current .pyenv-s if you rm -rf ~/.pyenv -- I did it to keep things simple but don't know if it's needed)
Now to test it out:
> python -m venv --upgrade-deps .venv
> which python ; which pip
So far so good, but if I create a foo.py that does import requests, and:
> pip install requests
> python foo.py
... I get "ModuleNotFoundError: No module named 'requests'"
Which is confusing.
An engineer suggested I inspect python -m site but I lost the original output.
Next I see at the bottom of my ~/.bash_profile:
# recommendation by homebrew from `brew install pyenv`
if which pyenv-virtualenv-init > /dev/null; then eval "$(pyenv virtualenv-init -)"; fi
export PYENV_ROOT="$HOME/.pyenv"
command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init -)"
Now I'm pretty sure the last time I installed pyenv (using homebrew) it suggested this, so I copy+pasted it into my ~/.bash_profile.
But it turns out I needed an additional:
eval "$(pyenv init --path)"
Now I restart my terminal and boom it works.
> pyenv init --path
PATH="$(bash --norc -ec 'IFS=:; paths=($PATH); for i in ${!paths[#]}; do if [[ ${paths[i]} == "'/Users/pi/.pyenv/shims'" ]]; then unset '\''paths[i]'\''; fi; done; echo "${paths[*]}"')"
export PATH="/Users/pi/.pyenv/shims:${PATH}"
command pyenv rehash 2>/dev/null
This appears to be removing any pyenv shims from the PATH env-var and prepending the correct shim to the PATH.
Now what about the original pyenv init - command? What does that do?
> pyenv init -
PATH="$(bash --norc -ec 'IFS=:; paths=($PATH); for i in ${!paths[#]}; do if [[ ${paths[i]} == "'/Users/pi/.pyenv/shims'" ]]; then unset '\''paths[i]'\''; fi; done; echo "${paths[*]}"')"
export PATH="/Users/pi/.pyenv/shims:${PATH}"
export PYENV_SHELL=bash
source '/Users/pi/.pyenv/libexec/../completions/pyenv.bash'
command pyenv rehash 2>/dev/null
pyenv() {
local command
command="${1:-}"
if [ "$#" -gt 0 ]; then
shift
fi
case "$command" in
activate|deactivate|rehash|shell)
eval "$(pyenv "sh-$command" "$#")"
;;
*)
command pyenv "$command" "$#"
;;
esac
}
This all seems confusing. The above is documented in https://github.com/pyenv/pyenv#advanced-configuration but do I really need such a complex path to achieve something that feels like it should be 'out-of-the-box'?

pyenv global x.x.x does not update the python version on linux

I have pyenv installed and have downloaded python versions 3.6.15 and 3.7.12. When I run
pyenv global 3.7.12
python -V
the output is: Python 3.10.2
pyenv versions gives the output
system
3.6.15
* 3.7.12 (set by /home/frege/.pyenv/version)
$ echo $PYENV_ROOT: /home/frege/.pyenv
$ which python: /user/bin/python
$ type python: python is hashed (/usr/bin/python)
I have the following in my .bashrc
export PATH="${HOME}/.pyenv/bin:$PATH"
eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"
I have restarted my terminal and $PATH contains
/home/frege/.pyenv/plugins/pyenv-virtualenv/shims:
/home/frege/.pyenv/bin:
...
/usr/bin:
What is wrong?

I understand that getting pyenv and virtualenvs to work together can be problematic. I came from virtualenvwrapper which makes working on virtual envs simple and I found pyenv a bit of a culture shock.
I have finally got my workflow sorted and I thought I would post it here as it might help someone. My OS is Manjaro.
I installed pyenv:
curl https://pyenv.run | bash
The following was added to .bashrc:
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/shims:${PATH}"
export PATH="$PYENV_ROOT/bin:$PATH"
export PYENV_VIRTUALENVWRAPPER_PREFER_PYVENV="true"
export WORKON_HOME=$HOME/.virtualenvs
eval "$(pyenv init -)"
pyenv virtualenvwrapper_lazy
(I have not seen the line export PATH="$PYENV_ROOT/shims:${PATH}" in many explanations, but it is critical in mine.)
To invoke a global version of python:
pyenv shell <version>
or
pyenv shell system
To create a virtual env:
pyenv virtualenv <version> <env name>
To activate the virtual environment:
pyenv activate <env name>
To deactivate the virtual environment:
source deactivate

pyenv: "python >virtual env name< not installed"

I am having trouble with pyenv after updating my macOS to 11.5. This is what I tried:
$ pyenv install 3.8.11 --skip-existing
$ pyenv virtualenv 3.8.11 >virtual env name<
$ pyenv local >virtual env name<
All of this works fine. Running pyenv local results in printing my virtual env's name. But I can't install dependancies or do anything with pip:
$ pip freeze
python >virtual env name< not installed
I tried following this answer, but I still have the same problem.
Note: This is also happening with virtual envs that were previously working pre-update.

Turns out the issue was with updating pyenv and not macOS. All I had to do was add the following lines to my ~./zshrc (or ~/.zprofile:
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init --path)"

How install and use different versions of pythons on MacOS using pyenv

Starting out when I run $ which python3 I get:
/Library/Frameworks/Python.framework/Versions/3.8/bin/python3
And in my .zprofile I have:
PATH="/Library/Frameworks/Python.framework/Versions/3.8/bin:${PATH}"
export PATH
So starting out, I have 3.8 installed and it works. Now, I need to create a setup that will allow me to install and use different versions of python for different projects.
So, I tried the following:
$ brew update
$ brew install pyenv
$ pyenv version
It printed out System. So, it only sees the python 2.7 that comes with macos. Then I tried:
$ pyenv install 3.9.1
$ pyenv install 3.8.7
$ echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n eval "$(pyenv init -)"\nfi' >> ~/.zshrc
$ source ~/.zshrc
Now, at the end of my .zshrc file I have:
if command -v pyenv 1>/dev/null 2>&1; then
eval "$(pyenv init -)"
fi
But I still just get System when I run $ pyenv version. I know the different python versions are getting installed in ~/.pyenv/versions directory. So, what else am I supposed to do to get it
to list all the versions and switch back and forth between them?

First off, for pyenv to work correctly, you should uninstall the Python that's in /Library/Frameworks/Python.framework/Versions/3.8/bin/python3 and remove it from your $PATH.
If you use pyenv to manage your Python versions, then you should not install Python in any other way. pyenv will update your path automatically as you switch Python version.
Next, you need to set pyenv‘s default Python version by doing
$ pyenv global 3.9.1
on the command line.
Finally, to switch Python versions, you can use
$ pyenv local 3.8.7
on the command line. Note, that setting the local Python is sticky and works on a per-directory basis. So, for each directory where you need a specific Python version, use this command once.
For more info, see https://github.com/pyenv/pyenv/blob/master/COMMANDS.md

Ubuntu 14.04 - Python 3.4 - pyenv: command Not Found

I am trying to create a virtual environment for Python 3.4 on a fresh install of Ubuntu Server 14.04. I following the instructions for the venv module at:
https://docs.python.org/3/library/venv.html#module-venv
I don't have a lot of Python 3.4 or Ubuntu experience.
When I type the command:
pyvenv testDir
I get back:
pyvenv: command not found
What is causing this?

Ubuntu 14.04 uses Python 2 by default, and the pyenv command does not exist in Python 2 out of the box.
You can, however, use virtualenv for the same purpose. You just need to install it!
You should:
Install Python 3 and virtualenv apt-get install -y python3 python-virtualenv
Create a Python 3 virtualenv: virtualenv -p $(which python3) testDir
Activate the virtual environment with source testDir/bin/activate

It's also possible to create virtualenv by python itself.
python3 -m venv myenv
see documentation https://docs.python.org/3/library/venv.html

It's in the package python3.4-venv (Linux Mint) or python3-venv (Ubuntu - I guess).
The advantages of venv over virtualenv are that (1) it's in vanilla Python3, (2) interpreter does retain tab-completion.

Edit the .bashrc file present in your home directory by adding below code and save the file:
# Load pyenv automatically by adding
# the following to ~/.bashrc:
export PATH="/home/'Enter systemname here'/.pyenv/bin:$PATH"
eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"
After this you can now run the following command:
exec $SHELL
Now pyenv works properly