Virtual environment using pip and venv

• I’m only taking down notes for this because I want to stop googling the same docs over and over again & eventually just memorize this lol
• Resource
  • https://packaging.python.org/en/latest/guides/installing-using-pip-and-virtual-environments/#create-and-use-virtual-environments

venv

• Creates a “virtual” isolated Python installation, like a disposable workshop
  • Allows you to manage separate package installations for different projects
  • When you switch projects, you can create a new virtual environment isolated from other virtual environments
• DO NOT upload any venv folders to Github
  • Instead just upload a list of the packages your project needs

python3 -m venv .venv # (1)
source .venv/bin/activate # (2)
which python # (3)
deactivate # (4)
rm -rf .venv # (5)

1. python3 -m venv .venv
   • Create a new virtual environment in a local folder named .venv
   • venv will create a virtual Python installation in the .venv folder
2. source .venv/bin/activate
   • Activate the virtual environment before installing/using packages
   • this allows you to put the virtual environment-specific python and pip executables into your shell’s PATH
   • While a virtual environment is activated, pip will install packages into that specific environment
3. which python
   • Confirm if the virtual environment is activated by checking the location of the python interpreter
   • If the virtual environment is active, the above command will output a filepath that includes the .venv directory by ending with the following .venv/bin/python
4. deactivate
   • Deactivate it (switching projects, leaving ur virtual environment etc)

• rm -rf .venv
  • Deleting the venv folder (common to delete them)
  • Bash commands
  • Make sure your requirements.txt file is up to date

📌venv vs docker

• venv
  • Primarily focuses only on isolating Python dependencies and versions for a specific project
• docker
  • Provides a containerization platform for packaging an entire application and its dependencies (including the operating system, libraries, and other software) into a self-contained unit called a container
  • Much stronger isolation than venv
• Basically (acc to this Stack Overflow post)
  • With a Python venv, you can easily switch between Python versions and dependencies, but you’re stuck with your host OS.
  • With a Docker image, you can swap out the entire OS - install and run Python on Ubuntu, Debian, Alpine, even Windows Server Core.

📌Why explicitly state python3 instead of python when creating venv?

• venv module is explicitly a python3 feature, it doesn’t exist on python 2
  • “Using the Python 3 interpreter, find its built-in venv module and run it.”

pip

• The reference Python package manager, used to install and update packages into a virtual environment
• If you pip install something in the venv, even if you deactivate and reactivate it again, all the installations & dependencies will remain

Examples of using pip

python3 -m pip install requests # (1)
python3 -m pip install 'requests==2.18.4' # (2)
python3 -m pip install --upgrade requests # (3)
python3 -m pip install -r requirements.txt # (4)
python3 -m pip freeze # (5)
python3 pip freeze > requirements.txt 
 
# Example of requirements.txt # (6)
requests==2.18.4
google-auth==1.1.0

• 📌-m flag
  • run a module as a script
  • -m pip install ... → Use Python to run the pip module as a program

1. python3 -m pip install requests
   • Installing the Requests library
2. python3 -m pip install 'requests==2.18.4'
   • Installing with a specific version
3. python3 -m pip install --upgrade requests
   • Upgrade packages in-place using the --upgrade flag (latest version & all of its dependencies)
4. python3 -m pip install -r requirements.txt
   • You can declare all dependencies in a requirements file instead of installing packages individually
   • Requirements file
     • files containing a list of items to be installed using pip install
5. python3 -m pip freeze
   • export a list of all installed packages and their versions
   • pip freeze command is useful for creating requirements files that can re-create the exact versions of packages installed in an environment
   • python3 pip freeze > requirements.txt
     • You can save all the current requirements and put them in a requirements file
     • Redirection - Manage Data Streams
6. Requirements.txt → a requirements file
   • If you don’t state a specific version, pip will install the latest stable version it can find in PyPI (Python Package Index)
     • This is actually not recommended (breaking changes) so just pin the version