How to use different python versions

Multiple Python versions on the same machine?

Is there official documentation on the Python website somewhere, on how to install and run multiple versions of Python on the same machine on Linux? I can find gazillions of blog posts and answers, but I want to know if there is a «standard» official way of doing this? Or is this all dependent on OS?

11 Answers 11

I think it is totally independent. Just install them, then you have the commands e.g. /usr/bin/python2.5 and /usr/bin/python2.6 . Link /usr/bin/python to the one you want to use as default.

All the libraries are in separate folders (named after the version) anyway.

If you want to compile the versions manually, this is from the readme file of the Python source code:

Installing multiple versions

On Unix and Mac systems if you intend to install multiple versions of Python using the same installation prefix (—prefix argument to the configure script) you must take care that your primary python executable is not overwritten by the installation of a different version. All files and directories installed using «make altinstall» contain the major and minor version and can thus live side-by-side. «make install» also creates $/bin/python3 which refers to $/bin/pythonX.Y. If you intend to install multiple versions using the same prefix you must decide which version (if any) is your «primary» version. Install that version using «make install». Install all other versions using «make altinstall».

For example, if you want to install Python 2.5, 2.6 and 3.0 with 2.6 being the primary version, you would execute «make install» in your 2.6 build directory and «make altinstall» in the others.

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How to Use Different Python Versions with Virtualenv

As a software engineer you are probably familiar with virtual environments virtualenv as a way of creating isolated Python environments for your projects Virtualenv makes it easy to manage dependencies and ensure that your code works correctly regardless of the Python version installed on your system

As a software engineer, you are probably familiar with virtual environments (virtualenv) as a way of creating isolated Python environments for your projects. Virtualenv makes it easy to manage dependencies and ensure that your code works correctly, regardless of the Python version installed on your system.

But what if you need to use a specific Python version for a particular project? Fortunately, virtualenv makes it easy to use different Python versions, and in this blog post, we will walk you through the process.

Step 1: Install the Required Python Version

Before you can use a specific Python version with virtualenv, you need to install that version on your system. There are several ways to do this, depending on your operating system.

For example, on Linux, you can use the package manager to install the required version. On Ubuntu, for instance, you can install Python 3.8 using the following command:

sudo apt-get install python3.8 

On macOS, you can use Homebrew to install Python 3.8 using the following command:

On Windows, you can download and install the required Python version from the official Python website.

Step 2: Create a Virtual Environment

Once you have installed the required Python version, you can create a virtual environment using virtualenv. To do this, open a terminal window and navigate to the directory where you want to create the virtual environment.

Then, enter the following command to create a new virtual environment:

virtualenv -p /path/to/python/version myenv 

Replace /path/to/python/version with the path to the installed Python version, and myenv with the name you want to give to your virtual environment.

For example, if you installed Python 3.8 in the default location on your system, you can create a virtual environment for that version using the following command:

virtualenv -p /usr/bin/python3.8 myenv 

This will create a new virtual environment named myenv that uses Python 3.8.

Step 3: Activate the Virtual Environment

Once you have created the virtual environment, you need to activate it to start using it. To do this, enter the following command in your terminal window:

This will activate the virtual environment and change your terminal prompt to indicate that you are now using the virtual environment.

Step 4: Install Packages

With the virtual environment activated, you can now install the packages required for your project. To do this, use the pip package manager as you normally would.

For example, to install the requests package, enter the following command:

This will install the requests package in your virtual environment.

Step 5: Deactivate the Virtual Environment

When you are finished working in the virtual environment, you can deactivate it using the following command:

This will return you to your system’s default Python environment.

Conclusion

Using virtualenv to create isolated Python environments is a best practice for software engineering. With the steps outlined in this blog post, you can easily use different Python versions with virtualenv, ensuring that your code works correctly regardless of the Python version installed on your system.

By following these steps, you can create separate environments for each project you work on, each with its own Python version and dependencies. This makes it easy to manage dependencies and ensure that your code works as expected, even if you need to work on multiple projects that require different Python versions.

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