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I am using Homebrew-installed pipenv to manage my virtual environments for Python projects. I navigate to my Python project's folder and use the pipenv shell command to activate the venv.

It has worked fine, until today when I noticed that I can't run my app.py from within the shell using the python3 app.py command. I get the ModuleNotFoundError: No module named 'flask' right from line 1.

When I run which python3 and which pip3, I see the expected response that specifies that I'm within my venv. When I run pip3 list, I only see pip, setuptools and wheel.

This is odd, because just very recently everything has worked fine (1-2 weeks ago?), and I'm positive that I personally didn't do anything that would mess with the libraries/requirements.

The Pipfile still lists all the requirements as expected. So how come they got deleted from my virtual environment?

I understand that I can just redownload all of the requirements; I'm just curious about why this happened in the first place.

UPDATE: I just realised that I did change the name of the folder which contains the project; I assume this is the cause. Since I've redownloaded the requirements already, does that mean I now have duplicates existing somewhere? If so, where?

AlexZ
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1 Answers1

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If you moved/renamed the folder where you created your virtual env, then the next time you try to activate the virtual env there, Pipenv will create a brand new virtual env. This is because Pipenv creates the actual virtual env folders based on the full path to the project directory. This is noted in the docs:

https://pipenv-fork.readthedocs.io/en/latest/install.html#virtualenv-mapping-caveat

  • Pipenv automatically maps projects to their specific virtualenvs.
  • The virtualenv is stored globally with the name of the project’s root directory plus the hash of the full path to the project’s root (e.g., my_project-a3de50).
  • If you change your project’s path, you break such a default mapping and pipenv will no longer be able to find and to use the project’s virtualenv.

Emphasis on the 3rd bullet. So it didn't delete your packages, it basically created a new one. You should have also seen a notice that it was creating a new one:

demo$ pipenv shell
Launching subshell in virtual environment...
...

(demo) demo$ 
exit
demo$ cd ..
~$ mv demo demo2
~$ cd demo2

demo2$ pipenv shell
Creating a virtualenv for this project...
...

(demo2) demo2$

That "Creating a virtualenv..." means it's creating a new one.

Now, on to:

does that mean I now have duplicates existing somewhere? If so, where?

It means you still have your previous virtual env folder somewhere, where you previously installed your packages. You can try using the --venv option to get the top-level directory where Pipenv creates all virtual env folders. In your new env:

(demo2) demo2$ pipenv --venv
/Users/gino.mempin/.venvs/demo2-4Y1NLH_X

As mentioned, the virtual env folder here is demo2-4Y1NLH_X, and the top-level folder is (for my case) .venvs. The default is something like /.local/share/ or whatever you set WORKON_HOME to (see Custom Virtual Environment Location). Just run the --venv for yourself.

You can try going there, and it will list all the virtual envs you have created:

(demo2) demo2$ ls /Users/gino.mempin/.venvs
demo-tSf-ZA7f
demo2-4Y1NLH_X
some-other-project-ABJaje5
another-project-8WUmE08m
...

Here, if you are lucky, you can find the name of your old folder, and then simply delete it if you want to cleanup. If you are unlucky, there'll be multiple folders with the same name, and you won't be able to tell which one was your old folder.

(demo2) demo2$ ls /Users/gino.mempin/.venvs
demo-tSf-ZA7f
demo-7I2ki6rH
demo-8WUmE08m
demo2-4Y1NLH_X

There is currently no way to get the full path to the original directly from the virtual env folder-hash itself. (See related: How to remove all pipenv virtualenvs when the directory was deleted?). There is also no way to reuse your old virtual env and copy it to your new one. But you don't need to anyway, creating virtual envs is inexpensive, just recreate it and reinstall all previous packages.

Gino Mempin
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