[Python] Create and manage a virtual environment (venv)

Hello, this is inusuki from the System Solutions Department

This time we will create a virtual environment using Python's venv

What is venv?

venv is a module added in version 3.3 for creating lightweight Python virtual environments on top of the base Python

Using virtual environments, you can install Python packages on a project-by-project basis, rather than system-wide

This means you can use different versions and packages for each project, and launch other projects without having to worry about dependency impacts

For creating virtual environments from version 3.5 onwards, it is recommended to use venv (as of August 2023)

venv --- Create virtual environments

Try making it yourself

Now let's try it out

If you are using version 3.3 or later, this is a standard feature, so no additional installation is required

This time, I am using Python 3.11.0 on Windows

 
python -V Python 3.11.0

Creating a virtual environment

For convenience, create a directory called test_dir and create a virtual environment in it

The command to create a venv (python -m venv) is the same on Linux

To simplify the management of virtual environments, we will create one named myenv1

 
mkdir test_dir cd test_dir python -m venv myenv1

Some columns have been hidden to make it easier to see, but the contents of venv are as follows.
Since we will only be focusing on usage this time, we will not go into details, but these are important directories/files for configuring a virtual environment, so please do not make any changes lightly.

 
ls myenv1 Directory: C:\Users\ichik\test_dir\myenv1 Mode LastWriteTime Name ---- ------------- ---- d---- 2023/08/28 13:30 Include d---- 2023/08/28 13:30 Lib d---- 2023/08/28 13:30 Scripts -a---- 2023/08/28 13:30 pyvenv.cfg

Activating the virtual environment

Activate the virtual environment with the following command:

After execution, if the environment name is displayed at the beginning of the prompt, activation was successful

.\myenv1\Scripts\Activate.ps1 (myenv1) PS C:\Users\ichik\test_dir>

*The commands differ depending on the execution environment, so please refer to the table below

While the environment name is displayed, the Python in the virtual environment will be executed instead of the base Python

Note that when you create a venv in the standard way, the Python version of the virtual environment is the same as the base Python version

 python -V Python 3.11.0 

As mentioned above, the packages in the virtual environment are independent, so you can simply install them as you like

Disabling the virtual environment

Deactivate the virtual environment with the following command:

(myenv1) PS C:\Users\ichik\test_dir> deactivate

If you no longer need the virtual environment, you can delete the directory

ex) I want to copy and reuse a virtual environment

For example, if you are using it on a different PC or sharing it with others for development, you would not copy and reuse the venv itself

Create a list of packages and share them along with the source code using git or similar

You can output a list of packages with the following command:

(myenv1) PS C:\Users\ichik\test_dir> python -m pip freeze > requirements.txt

Next, run the following command in the newly launched virtual environment to install the packages all at once

(myenv1) PS C:\Users\ichik\test_dir> python -m pip install -r requirements.txt

ex2) I want to start a virtual environment with a different version (Windows)

You can also install any version to launch a virtual environment with a different version

First, check the version you have installed

py --list -V:3.11 * Python 3.11 (64-bit) -V:3.9 Python 3.9 (64-bit)

This time we will start a new project using Python 3.9

py -3.9 -m venv pyenv39 .\pyenv39\Scripts\Activate.ps1

The virtual environment has been launched with a different version than the base!

(pyenv39) PS C:\Users\ichik\test_dir> python -V Python 3.9.13

Then, you can run the program in a different version by referencing the source code and requirements.txt and running pip install

summary

• venv is a module added in version 3.3 for creating lightweight Python virtual environments on top of the base Python
• Different projects can use different versions and packages
• You can launch other projects without having to worry about dependencies

Thank you for viewing