Python

Table of Contents generated with DocToc

• Links
• Installing Python on macOS
• Pyenv Commands
• Style Guides
  • Documenting Python Code

Communities

• PyData - A community for developers and users of open source data tools.
• Python User Group Austria

Links

• pytest - newer unit testing framework.

• unittest - unit testing framework.

• Structuring Your Project - suggested Python 3 project structure.

• Implementing an Interface in Python - informal and formal interfaces and abstract base classes.

• Data Classes - mutable named tuples with default values.

• PEP 8 – Style Guide for Python Code - Python code style recommendations.

• Python Developer’s Guide - The guide for developers of Python.

Installing Python on macOS

Note, that macOS comes with Python 2.7 pre-installed. If you are new to Python, I recommend using version 3 instead.

Further note, that I am managing my python installations using pyenv and I am developing code using JetBrains PyCharm. This combination leads to using pyenv in parallel with the Python built in venv … and looks strange to me. Probably I’ll find a better solution later.

To install Python 3 on macOS the following steps are recommended:

1. Install pyenv
   • Follow the instructions in Homebrew in macOS
   • Pay special attention to the verification step of Build Environment einrichten
   • Install the Python build dependencies linked in section D of Homebrew in macOS

2. The installation instructions end with installing a python version. Choose the version number of the latest stable Python build here (at the time of writing this was version 3.12): pyenv install 3.12.

3. Now you can switch the global python version to the installed one: pyenv global 3.12

4. Restart your shell and verify the python --version

Remember:

To re-activate the pre-installed python use pyenv global system

Please note that when using pip for installing Python applications, you may need to add $HOME/.local/bin to your $PATH.

Display the Current venv in Command Prompt

I am using Oh my ZSH with the Powerlevel9k theme. This allows printing the current venv as a part of the command prompt:

To set this up, do this in your ~/.zshrc (adopted from Stackoverflow):

plugins=(virtualenv)

POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(status virtualenv)

Caveats:

1. Add that plugin in addition to other plugins you have.
2. Requires the POWERLEVEL9K theme

Pyenv Commands

… are described in the Command Reference.

# Install the latest version 3.* (keep the existing installations)
pyenv install 3

# list currently installed versions
pyenv versions

# list common 2.x versions available (excludes other vendors)
pyenv install -l | grep '^\s*2\.' | sort -g

# activate a python version globally
pyenv global 3.10.3

# activate a python version just for this shell
pyenv shell 3.10.3

# activate a python version always for current folder
pyenv local 3.10.3

Style Guides

• PEP 8 - Style Guide for Python Code
• Google Python Style Guide

Documenting Python Code

• Python Developer’s Guide: Documenting Python

• PEP 257 - Docstring Conventions

• JetBrains PyCharm Guide: Documenting Code
• Google Python Styleguide: Docstrings
• numpy Styleguide: Docstring Standard
• sphinx.ext.napoleon: Support for NumPy and Google style docstrings

Interesting Packages

• GitHub: JulienPalard / Pipe - Pipelines / stream processing for python.
• Monkeypatching/mocking modules and environments - safely set/delete an attribute, dictionary item or environment variable, or to modify sys.path for importing.

Creating Packages

• Rogier van der Geer: A Practical Guide to Setuptools and Pyproject.toml - The “new” way of setting up python projects.
• Rogier van der Geer: A Practical Guide to Using Setup.py - An older way of setting up python projects.