Virtual Environments (venv)

What is a virtual environment

• Let's say we have 2 Projects that use different versions of FastAPI

• Let's say Project 2 uses a newer version of FastAPI than Project 1 and there are breaking changes between the 2 versions

• You have a problem now where you need 2 different versions of the FastAPI framework and you are not able to upgrade

This is where VENVs come into play

• This is an isolated environment that will not be affected by any other changes

• It is completely isolated to this project

Creating a Virtual Environment

• Navigate to the folder where you want to create the VENV

• Use the following command to set up the VENV

# For Windows:
py -3 -m venv <venv_name>

# Example:
py -3 -m venv venv

# For Unix/Linux:
python3 -m venv <name>

# Example:
python3 -m venv venv

Setting up VENV

Now that you have created the VENV you will need to select the interpreter located in:

/path/to/project/venv_name/Scripts/python.exe

• In our case we will be using VSCode

• Go to View --> Command Palette

• Go to Select interpreter

• Enter the path to the interpreter

# For Windows:
/path/to/project/venv_name/Scripts/python.exe

# For Unix/Linux:
/path/to/project/venv_name/bin/python

# or
/path/to/project/venv_name/bin/python3

This should be remembered every time you enter the project, but if it doesn't, repeat this process

Set up VENV to be used in Terminal

• Go to the project folder

• Enter the following line:

# For Windows CMD:
venv/Scripts/activate.bat

# For Windows Powershell:
venv/Scripts/Activate.ps1

# For Linux
source venv/bin/activate
# Note that you need to run this command every time
# you open the terminal

Note: If done correctly you should have a (venv)at the beginning of the terminal line

This will not work if you are using Git Bash for Windows

Set up requirements.txt

• Once you have installed everything that you need to get started within your VENV use the following command

pip freeze > requirements.txt

• If you are on another machine and require the installation of all dependencies use:

pip install -r requirements.txt