oxtay oxtay - 5 months ago 58
Python Question

Broken references in Virtualenvs

I recently installed a bunch of dotfiles on my Mac along with some other applications (I changed to iTerm instead of Terminal, and Sublime as my default text editor) but ever since, all my virtual environments have stopped working, although their folders inside .virtualenvs are still there and they give the following error whenever I try to run anything in them:

dyld: Library not loaded: @executable_path/../.Python
Referenced from: /Users/[user]/.virtualenvs/modclass/bin/python
Reason: image not found
Trace/BPT trap: 5


I have removed all the files related to dotfiles and have restored my .bash_profile to what it was before, but the problem persists. Is there any way to diagnose the problem or solve it in an easy way (e.g. not requiring to create all the virtualenvs all over again)?

Answer

I found the solution to the problem here, so all credit goes to the author.

The gist is that when you create a virtualenv, many symlinks are created to the Homebrew installed Python.

Here is one example:

$ ls -la ~/.virtualenvs/my-virtual-env
...
lrwxr-xr-x  1 ryan staff   78 Jun 25 13:21 .Python -> /usr/local/Cellar/python/2.7.7/Frameworks/Python.framework/Versions/2.7/Python
...

When you upgrade Python using Homebrew and then run brew cleanup, the symlinks in the virtualenv point to paths that no longer exist (because Homebrew deleted them).

The symlinks needs to point to the newly installed Python:

lrwxr-xr-x  1 ryan staff   78 Jun 25 13:21 .Python -> /usr/local/Cellar/python/2.7.8_1/Frameworks/Python.framework/Versions/2.7/Python

The solution is to remove the symlinks in the virtualenv and then recreate them:

find ~/.virtualenvs/my-virtual-env/ -type l -delete
virtualenv ~/.virtualenvs/my-virtual-env

It's probably best to check what links will be deleted first before deleting them:

find ~/.virtualenvs/my-virtual-env/ -type l

In my opinion, it's even better to only delete broken symlinks. You can do this using GNU find:

gfind ~/.virtualenvs/my-virtual-env/ -type l -xtype l -delete

You can install GNU find with Homebrew if you don't already have it:

brew install findutils

Notice that by default, GNU programs installed with Homebrew tend to be prefixed with the letter g. This is to avoid shadowing the find binary that ships with OS X.