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Python

  • Designed by Guido van Rossum in 1991

Installation

# MacOS comes with an old python version preinstalled, you can installed the newest one with brew
brew install python
brew ls python -v
which -a python3
python3 --version

Interpreter

  • CPython runs a Python code. To do that:
  • The code is compiled to bytecode by CPython
  • The compiled code is then interpreted by the Python Virtual Machine (PVM).

  • That means that python is both compiled and interpreted

  • You can configure your IDE to use a python interpreter (the python binary) with a specific version

  • The python binary can also be picked from your chosen virtual environment
  • On vscode, Python: Select Interpreter

CPython compiler step

  • When you run a Python code, CPython first compiles your source code (.py) into bytecode (.pyc)
  • This bytecode is stored at __pycache__/
  • The bytecode is not machine code. It's a lower-level, platform-independent representation of your code
  • Example:def add(a,b): return a+b becomes a handful of bytecode instructions like LOAD_FAST, BINARY_ADD, etc.

Python Virtual Machine (PVM) execution step

  • CPython then executes that bytecode using the Python Virtual Machine, which is part of the CPython runtime.
  • The PVM reads the bytecode instructions one by one and performs the corresponding machine-level operations.

Virtual Environment

  • Each virtual environment is created based on a python interpreter (version)
  • A virtual environment contains all libraries and binaries isolated from the operating system
  • Even the python binary is isolated (although symlinked to the system python binary)
  • Options
  • venv: the native virtual environment solution
  • virtualenv: 3rd party
  • pipenv: 3rd party, more recent
python -m venv ".venv"
source ./.venv/bin/activate
echo $VIRTUAL_ENV
echo $PATH
  • On vscode, to select the venv Python: Select Interpreter and select the venv or "Enter interpreter path..." and insert the absolute path of venv

Language Server

  • Jedi: Community-driven
  • Pylance: Developed by Microsoft
  • With homebrew, source files are installed at /opt/homebrew/Cellar/[email protected]/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12

Linter & Formatter

IDEs

  • Vscode extensions
  • ms-python.python
  • ms-python.debugpy
  • ms-python.vscode-pylance
  • charliermarsh.ruff
  • ms-toolsai.jupyter