Understanding the Need for Python 2.7 alongside Python 3 on Ubuntu
While Python 3 is the present and future of the language, there are still many applications and libraries that rely on Python 2.7. This necessitates the installation of both versions on a single system for developers who need to maintain or run legacy Python 2.7 code. Ubuntu, being a popular choice for developers, provides a straightforward way to manage multiple Python versions.
Preparing Ubuntu for Python 2.7 and Python 3 Installation
Before proceeding with the installation, it’s important to update and prepare the Ubuntu system. This ensures that all existing packages are up to date and that there are no conflicts during the installation process.
sudo apt update
sudo apt upgrade
After updating the system, you can install the necessary software that allows you to manage multiple Python versions on Ubuntu.
Installing Software Properties Common
The software-properties-common package provides an abstraction of the used apt repositories. It allows you to easily manage your distribution and independent software vendor software sources.
sudo apt install software-properties-common
Installing Python 2.7 on Ubuntu
With the system prepared, you can now proceed to install Python 2.7. It’s important to note that Python 2.7 has reached the end of its life, and it’s not recommended for starting new projects. However, for legacy code, it’s still necessary.
Using APT to Install Python 2.7
The Advanced Package Tool (APT) is the default package manager for Ubuntu. It simplifies the process of managing software by automating the retrieval, configuration, and installation of software packages.
sudo apt install python2.7
After the installation, you can verify it by checking the version of Python 2.7.
python2.7 --version
Setting Up pip for Python 2.7
pip is a package manager for Python that simplifies the process of installing and managing Python packages. For Python 2.7, you’ll need to install pip2.
sudo apt install python-pip
Once installed, you can use pip2 to manage Python 2.7 packages.
pip2 --version
Managing Multiple Python Versions with update-alternatives
Ubuntu’s update-alternatives system provides a way to manage multiple versions of a program through symbolic links. This is particularly useful when dealing with multiple Python versions.
Configuring Python Alternatives
To set up Python alternatives, you need to add each version of Python to the alternatives system and then configure the priority.
sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 2
With the alternatives configured, you can switch between Python versions using the update-alternatives command.
sudo update-alternatives --config python
Working with Virtual Environments
Virtual environments are a crucial tool for Python developers. They allow you to create isolated environments for different projects, ensuring that each project has its own dependencies and Python versions.
Creating a Virtual Environment for Python 2.7
To create a virtual environment for Python 2.7, you first need to install the virtualenv package.
sudo pip2 install virtualenv
Once installed, you can create a new virtual environment for Python 2.7.
virtualenv --python=python2.7 my_legacy_project_env
To activate the virtual environment, use the following command:
source my_legacy_project_env/bin/activate
Ensuring Compatibility and Transitioning to Python 3
While maintaining Python 2.7 projects, it’s important to plan for a transition to Python 3. Tools like 2to3 can help automate the process of converting Python 2 code to Python 3.
Using 2to3 for Code Conversion
The 2to3 tool comes with Python and can be used to convert existing Python 2 code to Python 3.
2to3 example.py
This will output the differences and can also apply the changes directly with the -w flag.
2to3 -w example.py
FAQ Section
Why is Python 2.7 still used despite Python 3 being available?
Python 2.7 is still used due to legacy systems and applications that were developed before the introduction of Python 3. These systems require maintenance and updates, which necessitates the continued use of Python 2.7.
Can Python 2.7 and Python 3 coexist on the same system?
Yes, Python 2.7 and Python 3 can coexist on the same system. Developers can use tools like update-alternatives and virtual environments to manage multiple versions of Python.
How do I switch between Python 2.7 and Python 3 on Ubuntu?
You can switch between Python 2.7 and Python 3 using the update-alternatives command or by activating the appropriate virtual environment for your project.
Is it safe to use Python 2.7 for new projects?
No, it is not recommended to use Python 2.7 for new projects as it has reached the end of its life and no longer receives security updates or support from the community.
What should I do if I have a Python 2.7 project?
If you have a Python 2.7 project, you should plan to migrate it to Python 3. Tools like 2to3 can assist in the conversion process, and testing will be necessary to ensure compatibility.
