Guide to setting up a virtualenv for PythonAnywhere Web apps¶
A virtualenv is a way to have your own private Python environment that has different versions of packages to the system default. You can have many virtualenvs, each with its own versions of installed packages. On PythonAnywhere, this is a great way to use newer (or older) versions of software than the ones we have installed.
One reason you might want to do this is to use a newer version of Django. For example in current "haggis" system image our system default is 4.0.6, but the latest version released by Django Team (as of September 2022) is 4.1.1. If you want to upgrade to that, a virtualenv makes it easy.
(If you're on our old system image, you'll be on an even earlier version of Django, so this guide is even more pertinent.)
TIP: If you are on old system image, you may also want to update it
Log in to PythonAnywhere, and create a new Web app:
- Go to the "Web" tab.
- Select the "Add a new web app" option on the left-hand side.
- If you have a Web Developer account, specify the domain you want your web app to appear on, then click "Next"
- Select the "Manual configuration" option from the list.
- Click "Next", and wait for the system to tell you that the web app has been created.
Now you can check that you have a web app -- go to yourusername.pythonanywhere.com in your browser to see the simple site we generate for you.
You may have noticed a Virtualenv path option. Let's go and create a virtualenv, so we have something to put in there.
Creating the virtualenv and installing (eg) django¶
Go to the "Consoles" tab and start a Bash console
14:50 ~ $ mkvirtualenv --python=python3.10 myproject
TIP: if you see an error saying
mkvirtualenv: command not found, check
You can check it works -- the prompt should gain the
(myproject) prefix, and you can check
which pip returns the
(myproject)14:51 ~ $ which pip /home/myusername/.virtualenvs/myproject/bin/pip
If it hasn't, you'll need to activate the virtualenv, like this:
You'll need to do this in any bash console when you're trying to install things to your virtualenv or run
otherwise you'll be trying to make changes to the system environment instead of your virtualenv.
Now install Django:
(myproject)14:51 ~ $ pip install django
(apologies if this takes a long time. We're working on speeding up disk I/O)
Now you can check it worked:
(myproject)15:02 ~ $ which django-admin /home/myusername/.virtualenvs/myproject/bin/django-admin (myproject)15:02 ~ $ django-admin --version 4.1.1
Start a new django project:
(myproject)15:02 ~ $ django-admin.py startproject mysite
Check it worked:
(myproject)15:02 ~ $ tree mysite mysite ├── manage.py └── mysite ├── __init__.py ├── settings.py ├── urls.py └── wsgi.py
Using the virtualenv in your web app¶
Now go back to the Web tab and edit the WSGI file for your web app (There's a link on the web app tab) and delete everything except the Django section and then uncomment the Django section. Your WSGI file should look something like this:
# +++++++++++ DJANGO +++++++++++ # To use your own django app use code like this: import os import sys # assuming your django settings file is at '/home/myusername/mysite/mysite/settings.py' path = '/home/myusername/mysite' if path not in sys.path: sys.path.insert(0, path) os.environ['DJANGO_SETTINGS_MODULE'] = 'mysite.settings' # serve django via WSGI from django.core.wsgi import get_wsgi_application application = get_wsgi_application()
Then, back on the web tab itself, edit the path to your virtualenv in the Virtualenv section. You can specify the full path, /home/myusername/.virtualenvs/myproject, or just the short name of the virtualenv, myproject, and the system will automatically expand it to the full path after you submit it.
Save it, then go and hit the Reload button for your domain.
Checking it worked.¶
Go to site -- you should see the Django "it worked!" page.
You're all set up, and now you can use your virtualenv
Don't forget, the virtualenv has its own set of installed packages -- so if you
want to use something you'll need to
pip install it. A common example for
Django is the Python MySQL library.
For Python 2.7 you'll need to install
(myproject)15:12 ~/mysite $ pip install mysql-python
For Python 3.x you need a different package,
(myproject)15:12 ~/mysite $ pip install mysqlclient
Developing with your virtualenv¶
Remember: whenever you want to get back and work on your virtualenv, you need to make sure it's active -- if you're opening a new console, for example.
Look out for the little
(myproject) prefix at the command-line.
It's also well worth checking
which pip to make sure you're using the virtualenv pip when installing.
If in doubt, run:
(myproject)17:02 ~ $ source virtualenvwrapper.sh
To switch on virtualenvwrapper (you can add this to your
.bashrc if it's not there already)
17:02 ~ $ workon myproject
to switch to working on your virtual environment.