![]() News about the dynamic, interpreted, interactive, object-oriented, extensible programming language Python If you are about to ask a question, please consider. Homework-style questions will be removed, and you'll be encouraged to post there instead. Please don't use URL shorteners. Reddit filters them out, so your post or comment will be lost. Activating a virtual environment is really just adjusting some environment variables, such as PATH and PYTHONHOME, and deactivating is just setting them back to what they were before. The environment is per-process. Home Linux distributions How To Install virtualenv And virtualenvwrapper In Ubuntu. How To Install virtualenv And virtualenvwrapper. Is a bash script. The default activate script for Python’s virtualenv had some problems that bugged me: Create a new virtual environment, install virtualenv-activator inside it, and. Bash activate_shell.sh The script is being run. How to activate python virtual environment by shell script. How to source virtualenv activate in a Bash script. ![]() If you spawn a sub-process, it inherits a copy of the parent process' environment. Any changes made by the child affect that copy only, and evaporate when the process terminates, having no effect on the the parent process. Consequently, you can't edit environment variables of a process by spawning a sub-process. That's why the activate command has to be sourced, not executed, and it's why the deactivate command is actually a shell function, not a program/script that is executed, because it can't be. Okay after your comments, I modified my code. So now, I only create the virtualenv and I call directly python and pip from this directory '/path/to/venv/bin' Moreover, before calling the commands, I changed the current PATH to set at the first position the virtualenv bin directory. I hope it will be enough to not mess up the default python installation. To sum up: os.environ['PATH'] = '/path/to/venv/bin/' + os.pathsep + os.environ.get('PATH', ') subprocess.Popen(['/path/to/venv/bin/pip', 'install', 'setuptools']) subprocess.Popen(['/path/to/venv/bin/python', 'script.py']) Do I need to set others var env to ensure that any python commands called inside the script.py will use the one from the virtualenv bin directory? By the way, if you use pip from the virtualenv, be careful of path to long to have access the pip executable (see Issue: ). ![]() I've spent long hours to understand that I was facing this problem. No further changes should be needed, actually in all cases it has worked for me even without having to change the PATH. After searching around a bit it looks like you do need to change it though if the script you are starting also tries to Popen new python processes and these should run inside the virtualenv. If you are using Popen as in your example you should use subprocess.call instead since Popen will not wait for the process to finish, if this is just a result of the example being stripped down then ignore this. • ENV/lib/ and ENV/include/ are created, containing supporting library files for a new virtualenv python. Packages installed in this environment will live under ENV/lib/pythonX.X/site-packages/. • ENV/bin is created, where executables live - noticeably a new python. Thus running a script with #! /path/to/ENV/bin/python would run that script under this virtualenv’s python. • The crucial packages and are installed, which allow other packages to be easily installed to the environment. This associated pip can be run from ENV/bin/pip. The python in your new virtualenv is effectively isolated from the python that was used to create it. $ source bin/activate For some shells (e.g.
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