Use of Virtual Environments in Python Projects:

• Virtual Environment is used to separate out the versions of packages for eg., Django or Flask.
• In general, if we install Packages directly without Virtual Environment then they will be installed on global levels
• If you have multiple Django projects where some older projects need previous versions of Django and when you need a new project with the latest version of Django package and if you install it without virtual env then your older projects would be affected since the older version of Django package will be replaced with newer version after the upgrade.
• Hence it is best practice to use Virtual Env for each project and have whatever packages are needed for that particular project inside the virtual environment.
• venv is recommended for creating Virtual Environments from Python 3.5
• Create a folder for the new project then cd to the folder and execute below to create new virtual env

Creating Virtual Env:

cd to your project folder

Linux:

sudo apt install python3-pip to install pip if not already present.

Now install a tool for creating isolated virtual python environments or you can use venv that comes directly with Python installation

pip install virtualenv

virtualenv env_name or python3 -m venv env_name

this will create a new folder(env_name) in your current directory

To activate a virtual environment

source env_name/bin/activate

After activation, you would see a change similar to (venv) C:\Users\Name\Folder>

deactivate -- to deactivate the venv

Windows:

python -m venv env_name -- to create Virtual Environment

env_name\scripts\activate -- to activate

deactivate -- to deactivate

other info:

Do not store any project scripts inside 'env_name' folder

pip list -- to get a list of packages installed in the current venv

pip freeze -- to get a list of packages in a format usable to copy for requirements.txt

command to create a requirements.txt file with a list of packages installed in the current project pip freeze > requirements.txt

To directly install all packages from the requirements.txt use pip install -r requirements.txt