Problem with virtualenv in Mac OS X

I’ve run across this problem myself. I wrote down the instructions in a README, which I have pasted below….

I have found there are two things that work:

1. Make sure you’re running the latest virtualenv (1.5.1, of this writting)

2. If you’re using a non system Python as your standard Python (which python to check) Forcefully use the System supplied one.

   Instead of virtualenv thing use /usr/bin/python2.6 PATH/TO/VIRTUALENV thing (or whatever which
python returned to you – this is what it did for me when I ran into this issue)

I had the same problem and as I see it now, it was caused by a messy Python installation. I have OS X installed for over a year since I bought a new laptop and I have already installed and reinstalled Python for several times using different sources (official binaries, homebrew, official binaries + hand-made adjustments as described here). Don’t ask me why I did that, I’m just a miserable newbie believing everything will fix itself after being re-installed.

So, I had a number of different Pythons installed here and there as well as many hardlinks pointing at them inconsistently. Eventually I got sick of all of them and reinstalled OS X carefully cleaned the system from all the Pythons I found using find utility. Also, I have unlinked all the links pointing to whatever Python from everywhere. Then I’ve installed a fresh Python using homebrew, installed virtualenv and everything works as a charm now.

So, my recipe is:

sudo find / -iname "python*" > python.log

Then analyze this file, remove and unlink everything related to the version of Python you need, reinstall it (I did it with homebrew, maybe official installation will also work) and enjoy. Make sure you unlink everything python-related from /usr/bin and /usr/local/bin as well as remove all the instances of Frameworks/Python.framework/Versions/<Your.Version> in /Library and /System/Library.

It may be a dirty hack, but it worked for me. I prefer not to keep any system-wide Python libraries except pip and virtualenv and create virtual environments for all of my projects, so I do not care about removing the important libraries. If you don’t want to remove everything, still try to understand whether your Pythons are, what links point to them and from where. Then think what may cause the problem and fix it.

On on OSX 10.6.8 leopard, after having “upgraded” to Lion, then downgrading again (ouch – AVOID!), I went through the Wolf Paulus method a few months ago, completely ignorant of python. Deleted python 2.7 altogether and “replaced” it with 3.something. My FTP program stopped working (Fetch) and who knows what else relies on Python 2.7. So at that point I downloaded the latest version of 2.7 from python.org and it’s installer got me up and running – until i tried to use virtualenv.

What seems to have worked for me this time was totally deleting Python 2.7 with this code:

sudo rm -R /System/Library/Frameworks/Python.framework/Versions/2.7

removing all the links with this code:

sudo rm /usr/bin/pydoc
sudo rm /usr/bin/python
sudo rm /usr/bin/pythonw
sudo rm /usr/bin/python-config

I had tried to install python with homebrew, but apparently it will not work unless all of XTools is installed, which I have been avoiding, since the version of XTools compatible with 10.6 is ancient and 4GB and mostly all I need is GCC, the compiler, which you can get here.

So I just installed with the latest download from python.org.

Then had to reinstall easy_install, pip, virtualenv.

Definitely wondering when it will be time for a new laptop, but there’s a lot to be said for buying fewer pieces of hardware (slave labor, unethical mining, etc).

Like @RyanWilcox mentioned, you might be inadvertently pointing virtualenv to the wrong Python installation. Virtualenv comes with a -p flag to let you specify which interpreter to use.

In my case,

virtualenv test_env

threw the same error as yours, while

virtualenv -p python test_env

worked perfectly.

If you call virtualenv -h, the documentation for the -p flag will tell you which python it thinks it should be using; if it looks wonky, try passing -p python. For reference, I’m on virtualenv 1.11.6.

I ran into a variation of this “not functioning” error.
I was trying to create an environment in a folder that included the path “…/Programming/Developing…” which is actually “/Users/eric/Documents/Programming:Developing/”

and got this error:

ImportError: No module named site
ERROR: The executable env/bin/python2.7 is not functioning
ERROR: It thinks sys.prefix is u'/Users/eric/Documents/Programming:Developing/heroku' (should be u'/Users/eric/Documents/Programming:Developing/heroku/env')
ERROR: virtualenv is not compatible with this system or executable

I tried the same in a different folder and it worked fine, no errors and env/bin has what I expect (activate, etc.).

The above solutions failed for me, but the following worked:

python3 -m venv --without-pip <ENVIRONMENT_NAME>
. <ENVIRONMENT_NAME>/bin/activate
curl https://bootstrap.pypa.io/get-pip.py | python
deactivate

It’s hacky, but yes, the core problem really did just seem to be pip.

In case anyone in the future runs into this problem – this is caused by your default Python distribution being conda. Conda has it’s own virtual env set up process but if you have the conda distribution of python and still wish to use virtualenv here’s how:

1. Find the other python distribution on your machine: ls -ls /usr/bin/python*

2. Take note of the availble python version that is not conda and run the code below (note for python 3 and above you have to upgrade virtualenv first): virtualenv -p python2.7(or your python version) flaskapp

I did the following steps to get virtualenv working :

Update virtualenv as follows :

==> sudo pip install --upgrade virtualenv

Initialize python3 virtualenv :

==> virtualenv -p python3 venv

Just in case there’s someone still seeking for the answer.

I ran into this same problem just today and realized since I already have Anaconda installed, I should not have used pip install virtualenv to install virtual environment as this would give me the error message when trying to initiate it later. Instead, I tried conda install virtualenv then entered virtualenv env_mysite and problem solved.

Open terminal and type /Library/Frameworks/Python.framework/Versions/

then type ls /Library/Frameworks/Python.framework/Versions/2.7/bin/
if you are using Python2(or any other else).

Edit ~/.bash_profile and add the following line:
export PATH=$PATH:/Library/Frameworks/Python.framework/Versions/2.7/bin/

cat ~/.bash_profile


In my case the content of ~/.bash_profile is as follows:

export PATH=$PATH:/Library/Frameworks/Python.framework/Versions/2.7/bin/

Now the virtualenv command should work.

I had this same issue, and I can confirm that the problem was with an outdated virtualenv.py file.

It was not necessary to do a whole install –upgrade.

Replacing the virtualenv.py file with the most recent version sufficed.

I also had this problem, and I tried the following method which worked for me:

conda install virtualenv

virtualenv --system-site-packages /anaconda/envs/tensorflow (here envs keeps all the virtual environments made by user)

source /anaconda/envs/tensorflow/bin/activate

Hope it’s helpful.

I got the same problem and I found that it happens when you do not specify the python executable name properly. So for python 2x, for example:

virtualenv --system-site-packages -p python mysite

But for python 3.6 you need to specify the executable name like python3.6

virtualenv --system-site-packages -p python3.6 mysite

I had this same issue when trying to install py2.7 on a newer system. The root issue was that virtualenv was part of py3.7 and thus was not compatible:

$  virtualenv -p python2.7 env
Running virtualenv with interpreter /usr/local/bin/python2.7
New python executable in /Users/blah/env/bin/python
ERROR: The executable /Users/blah/env/bin/python is not functioning
ERROR: It thinks sys.prefix is u'/Library/Frameworks/Python.framework/Versions/2.7' (should be u'/Users/blah/env')
ERROR: virtualenv is not compatible with this system or executable

$ which virtualenv
/Library/Frameworks/Python.framework/Versions/3.7/bin/virtualenv

# install proper version of virtualenv 
$ pip2.7 install virtualenv

$ /Library/Frameworks/Python.framework/Versions/2.7/bin/virtualenv -p python2.7 env

$ . ./env/bin/activate
(env) $