Python

Conventions

• PEP 8 styling guideline walkthrough
  • Using the flake8 linter - checks for errors (including failing to comply with PEP 8 guidelines
• Meaning and naming conventions around single and double underscores

Imports

• Recap on imports, absolute vs relative imports
• Python 2 vs 3 imports

Pip

Package installer.

Command	Description
pip install <package>	Install the latest version of a package
pip install <package>==<version>	Install the specified version of a package
pip install -r requirements.txt	Install the packages from a requirements.txt file
pip list --outdated	View outdated packages
pip install --upgrade <package>	Upgrade the desired packages
pip uninstall <package>	Uninstall a package

If pip has not been added to the path, replace pip with python -m pip in the commands above.

Pyenv

Easily switch between multiple versions of Python.

• Installation
• Commands reference

Scripting

• Built-in library for command-line parsing: argparse tutorial
• Built-in library for logging: logging tutorial
• Testing framework: PyTest tutorial
• Built-in exceptions
• Regular expressions tutorial
• Top data science libraries

Virtual Environments

Bundle all the packages and their versions to run an application so that they do not conflict with the globally installed python packages.

1. Create virtual environment directory (suggested name: .venv).

   Windows Linux

   py -m venv .venv
   

   python3 -m venv .venv
   

2. Activate virtual environment. Use the active shell's corresponding activate script.

   Windows Powershell Linux

   .venv\Scripts\Activate.ps1
   

   source .venv/bin/activate
   

3. Install the required packages: pip section

4. Create/update the requirements.txt file (to record the versions of packages used in the project)

   pip freeze > requirements.txt
   

5. Exit the virtual environment

   deactivate
   

VS Code integration

After selecting .venv/bin/python to be the Python interpreter, terminals and debuggers will run in the virtual environment by default.

Resources

• Virtual Environments and Packages

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Last update: February 5, 2022