{"id":538,"date":"2019-09-29T23:56:27","date_gmt":"2019-09-29T15:56:27","guid":{"rendered":"https:\/\/www.techcoil.com\/blog\/?p=538"},"modified":"2021-06-04T11:42:38","modified_gmt":"2021-06-04T03:42:38","slug":"how-to-use-python-3-virtual-environments-to-run-python-3-applications-on-your-raspberry-pi","status":"publish","type":"post","link":"https:\/\/www.techcoil.com\/blog\/how-to-use-python-3-virtual-environments-to-run-python-3-applications-on-your-raspberry-pi\/","title":{"rendered":"How to use Python 3 virtual environments to run Python 3 applications on your Raspberry Pi"},"content":{"rendered":"

Whenever I am working on a Python 3 project, I will always use a Python 3 virtual environment for running that project. Therefore, I tend to do the same when it comes to building Python 3 applications to run on a Raspberry Pi<\/a>. <\/p>\n

If you are looking to build Python 3 applications to run on your Pi, then you may find this article useful for you.<\/p>\n

Why should we run our Python 3 application in a virtual environment on the Raspberry Pi?<\/h2>\n

Since a virtual environment helps us isolate Python dependencies within an application runtime, we will be able to run applications with conflicting dependencies on the same Raspberry Pi. <\/p>\n

Although we can use Docker<\/a> to isolate our applications with containers, Python 3 virtual environments are more light-weight for Raspberry Pi.<\/p>\n

How to install python3-venv on your Raspbian<\/h2>\n

If python3-venv<\/code> is not available on your Raspbian, then you will need to run the following command in a terminal program to install it:<\/p>\n

\r\nsudo apt-get install python3-venv -y\r\n<\/pre>\n
Running the command to create a Python 3 virtual environment<\/h2>\n
However, if python3-venv<\/code><\/a> is available on your Raspberry Pi, then you can create a Python 3 virtual environment. For example, if I want to create a virtual environment within the my_venv<\/code> directory in the home directory of the current user, then I will run the following command:<\/p>\n
\r\npython3 -m venv ~\/my_venv\r\n<\/pre>\n
After the command had completed, a directory named as my_venv<\/code> will be created in the  home directory of the current user.<\/p>\n
If you see the following output:<\/p>\n
\r\nThe virtual environment was not created successfully because ensurepip is not\r\navailable.  On Debian\/Ubuntu systems, you need to install the python3-venv\r\npackage using the following command.\r\n\r\n    apt-get install python3-venv\r\n\r\nYou may need to use sudo with that command.  After installing the python3-venv\r\npackage, recreate your virtual environment.\r\n\r\nFailing command: ['\/home\/pi\/my_venv\/bin\/python3', '-Im', 'ensurepip', '--upgrade', '--default-pip']\r\n<\/pre>\n
then you will need to install python3-venv<\/a>.<\/p>\n
What is inside the ~\/my_venv directory?<\/h3>\n
If you look into the directory that was created by the python3-venv<\/code> module, you will find everything that is needed to make the terminal session run within an isolated Python 3 environment. Any Python 3 dependencies that are installed for this virtual environment will be contained within this directory.<\/p>\n
How to activate the Python 3 virtual environment on your Raspberry Pi<\/h2>\n
Before you can do anything with that Python 3 virtual environment, you will need to activate it first. In order to activate the Python 3 virtual environment, you need to use the source<\/code> command to load activate.sh<\/code> into the current shell session:<\/p>\n
\r\nsource ~\/my_venv\/bin\/activate\r\n<\/pre>\n
After you had done so, you will notice that the shell prompt got appended with the name of your Python 3 virtual environment:<\/p>\n
\r\n(my_venv) pi@raspberrypi:~ $ \r\n<\/pre>\n
This meant that the Python 3 virtual environment had been activated in your current terminal session. If you want to verify that, then you can run the following commands:<\/p>\n
\r\nwhich python\r\nwhich pip\r\n<\/pre>\n
When the commands complete, you should see the following output:<\/p>\n
\r\n\/home\/pi\/my_venv\/bin\/python\r\n\/home\/pi\/my_venv\/bin\/pip\r\n<\/pre>\n
Notice that the two binaries came from the Python 3 virtual environment directory that you had just created.<\/p>\n
In addition to that, you can check the Python 3 dependencies that is included within your Python 3 virtual environment:<\/p>\n
\r\npip list\r\n<\/pre>\n
When you do so, you may find output similar to the following:<\/p>\n
\r\nPackage       Version\r\n------------- -------\r\npip           18.1   \r\npkg-resources 0.0.0  \r\nsetuptools    40.8.0 \r\n<\/pre>\n
How to install Python 3 dependencies into the virtual environment<\/h2>\n
Once you had activated your virtual environment, you can then install whatever dependencies that your Python 3 application will need with the pip<\/code> command. For example, I can run the following command to install Flask into my virtual environment:<\/p>\n
\r\npip install flask\r\n<\/pre>\n
After the command complete, you will then be able to run a Python 3 application that uses Flask to realise a web server on your Raspberry Pi. You can verify the pip installation with the following command:<\/p>\n
\r\npip list\r\n<\/pre>\n
After the command had completed, you should find new entries in the output:<\/p>\n
\r\nPackage       Version\r\n------------- -------\r\nClick         7.0    \r\nFlask         1.1.1  \r\nitsdangerous  1.1.0  \r\nJinja2        2.10.1 \r\nMarkupSafe    1.1.1  \r\npip           18.1   \r\npkg-resources 0.0.0  \r\nsetuptools    40.8.0 \r\nWerkzeug      0.16.0 \r\n<\/pre>\n
Running a Python 3 application within your virtual environment<\/h2>\n
Suppose that you had created a Python 3 script at ~\/run_app.py<\/code> with the following content:<\/p>\n
\r\nfrom flask import Flask\r\n\r\napp = Flask(__name__)\r\n\r\napp.route('\/')\r\ndef index():\r\n\treturn 'Welcome to my Flask server running on my Raspberry Pi', 200\r\n\r\napp.run('0.0.0.0', 12345)\r\n<\/pre>\n
When you want to run this application, you can use the python<\/code> command from the virtual environment to do so:<\/p>\n
\r\npython ~\/run_app.py\r\n<\/pre>\n
After you had ran the command, you should see the following output in your shell terminal:<\/p>\n
\r\n * Serving Flask app "run_app" (lazy loading)\r\n * Environment: production\r\n   WARNING: This is a development server. Do not use it in a production deployment.\r\n   Use a production WSGI server instead.\r\n * Debug mode: off\r\n * Running on http:\/\/0.0.0.0:12345\/ (Press CTRL+C to quit)\r\n<\/pre>\n
Press CTRL+C to stop the Flask application.<\/p>\n
Deactivating the virtual environment<\/h2>\n
When you want to exit from the virtual environment, you can run the following command:<\/p>\n
\r\ndeactivate\r\n<\/pre>\n
After you had done so, the shell prompt returns back to how it was before you activate the virtual environment:<\/p>\n
\r\npi@raspberrypi:~ $ \r\n<\/pre>\n
At this point in time, when you run the following commands:<\/p>\n
\r\nwhich python\r\nwhich pip\r\n<\/pre>\n
you may find the following output:<\/p>\n
\r\n\/usr\/bin\/python\r\n<\/pre>\n
Since I am running this examples from Raspbian lite, the pip<\/code> is not installed by default. Given these points, you can be sure that your current shell terminal had deactivated the Python 3 virtual environment<\/p>\n
Summing up<\/h2>\n
In summary, you will typically go through the following steps to use Python 3 virtual environments to run your application on your Raspberry Pi:<\/p>\n