Copier template for python

Opinionated copier template for Flowtale python projects.

Features

Task	Tool
Testing framework	pytest, unittest
Test mocking	pytest-mock
Pre-commit hooks	pre-commit
Version management	bump2version
Environment management	direnv
Common style	EditorConfig
Editor configuration	vscode with suggested extensions
Autoformatters	black with experimental string processing (--preview), pydocstyle
Linters	flake8, pydocstyle
Test and packaging	gitlab-ci
Run common commands	make

Automatisms

On save (vscode)

• Code formatted with black
• Import sorted with isort

On commit

pre-commit is executed automatically before each commit in order to prevent code that does not follow the project guidelines. Depending on the user configuration either only the standard checks or all the checks are run on commit.

Some pre-commit hooks modify the files. Re-stage them after the modification.

Standard checks:

• Check for big file added to commit
• Check for committed secrets

Strict checks:

• Trailing whitespaces removed
• Add newline at the end of the file
• flake8 linter executed
• black formatter executed
• isort import sorted executed
• pydocstyle docstring checker executed

Linter plugins

Name	Description	strict
flake8-builtins	Check for python builtins being used as variables or parameters.
pep8-naming	Check your code against PEP 8 naming conventions.
flake8-pytest-style	Check for common style issues or inconsistencies with pytest-based tests.
flake8-print	Forbids print in the code besides cli.py (use logging!)	x
flake8-eradicate	Find commented out (or so called "dead") code.	x
flake8-bugbear	Find likely bugs and design problems in your program	x
flake8-annotations	Find missing type annotations	x

On push

• Tests and run all the pre-commit checks on all files executed on the CI

Setup

Dependencies

Dependencies to create the project template with copier

• python (suggested install method: system)
• copier (suggested install method: pipx)

Dependencies for the project

• poetry
• pyenv (recommended)

Development environment configuration

These configurations are required to setup the development environment and need to be performed only once.

poetry

(Recommended) To make poetry use the python interpreter of pyenv (defined in the .python-version file inside the project)

poetry config virtualenvs.prefer-active-python true

This setting allows to easier to rename the project folder without having to recreated the virtual environment. It also makes vscode automatically detected the poetry virtual environment (see VScode)

pyenv (recommended)

This step can be skipped if the system python version always matches the version specified in the .python-version of the project (very unlikely).

Add the following to ~/.bashrc or ~/.zshrc to initialize pyenv

export PYENV_ROOT="$HOME/.pyenv"
command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init -)"

direnv (recommended)

direnv is a tool that enables automatic loading and unloading of directory-specific environment variables. It is useful to automatically activate the virtual environment and load any project specific environment variables when entering a project folder. Because this template expects the use of poetry, the .envrc file accompanying the template includes a function to automatically load a poetry virtual environment, and will also load project specific environment variables from any present .env file with the dotenv command.

To make use of direnv, make sure it is installed. Go to the project root directory (where the .envrc file is located) and run direnv allow.

Usage

Project initialization

1. Create a new project based on this copier template (it can also be applied to existing projects)

   copier copy https://github.com/flowtaleai/copier-python-poetry.git project-folder

   The template version used corresponds to the most recent tag of the template repository.

2. Answer all the questions to configure the project (see Copier parameters)

3. Commit all the files

   cd pythonboilerplate
   git init
   git add .
   git commit -m "Initial commit"

4. Generate the poetry lock file

   poetry install

5. Commit the lock file

   git add poetry.lock
   git commit -m "Poetry lock file regenerated"

   (Opinion) It is always better to commit the lock file by itself given that reverting a commit with an update to the lock file is complicated.

6. Follow the project README to configure the project development environment

Project update

1. From within a project folder that has already been initialized with the template run

   copier update --skip-answered

   This will update our project with the version corresponding to the most recent tag of the template. It will perform a three way merge between out project and the newest changes introduced by the template.

   Do not provide the --skip-answered flag if you want to change some of the original answers.

2. Run poetry lock to regenerate the poetry lock file given that the pyproject.toml may have been updated

3. Run poetry install --sync to update the project dependencies

Copier parameters

Name	Example	Description
author_name	Team Faboulous
author_email	teamfaboulous@mycompany.com
distribution_name	awsome-project	Used to define the name of the python distribution
package_name	awsomeproject	Used to define the name of the python package
project_name	Awsome Project	Name of the project
repository_name	awsome-project	Name of the project repository
project_short_description	A fantastic new project	Description of the project. Also used in the CLI help.
version	0.1.0	SemVer 2.0 version
license	MIT	Project license
package_type	cli	If cli generate cli module with argument parser and cli entrypoint
python_version	3.10	Define the python version to use for pyenv and the CI pipelines
testing_framework	pytest	Python testing framework
max_line_length	88	Code max line length
use_flake8_strict_plugins	true	If true install flake8 plugins that allow to catch bugs, security vulnerabilities and apply more strict rules. They can be a bit overwhelming.
ide	vscode	Define the IDE(s) used by the developers.
git_hosting	gitlab	Define GIT hosting that will be used.
use_jupyter_notebooks	true	If true install ipykernel dependency
generate_example_code	true	If true generate example files and code snippets
strip_jupyter_outputs	true	If true strip output from Jupyter notebooks before committing

Project usage

python dependencies

• Do not manually change the dependency specification of the python packages related to the copier template (i.e. do not change the version in pyproject.toml). These will be automatically updated when we apply an update of the copier template.

VSCode

• VSCode should automatically detect the virtual environment if poetry is configured to store the venv in a subfolder of the project (it is by default).
• Otherwise manually select the interpreter with Python: Select interpreter
  • Run poetry run poetry env info -p to discover where it is located

Shell

• To perform actions in the shell

  • explicitly activate the virtual environment

    poetry shell

  • Or run commands in the virtual environment

    poetry run COMMAND

Style suggestions

• Docstrings convention is google without types (types are specified using standard python typing)
• Use pathlib.Path instead of str for file names
• Use pathlib.Path to process files instead of os

Contributing

• The python dependencies in the template should be update periodically

  • Updating the major version of black may require reformatting large portions of a project codebase to make the CI lint stage pass

• A note to the [Rationale][#rationale] section should be added if it helps explaining non-obvious choices

Versioning

• This project is tagged with versions according to SemVer.

• The version has a format MAJOR.MINOR.PATCH, which in the context of this project means:

  • Major: Changes that modify the generated project structure or components significantly in a way that is not backward-compatible.
    • e.g. updating the black major version
    • e.g. add a required flake8 plugin that may cause the CI pipeline of an existing project to fail
  • Minor: Additions or enhancements to the template that do not alter the existing structure in a backward-incompatible way.
    • e.g. add support for generating the documentation
  • Patch: Fixes to issues or bugs in the template that do not affect the generated project's structure or compatibility.

• To bump the project version:

make bump

​ and select the part of the version to bump

Rationale

• [2023-10-10] We pass the --preview flag to black 23.x in particular to format long strings. The effects of --preview should be re-evaluated at each major version update of black.

  # before formatting
  myvar = "Loooong ... string"
  
  # after formatting
  myvar = (
      "Loooong ..."
      "... string"
  )

• The versions of python dependencies of the tools (black, flake, ...) are managed by the copier template and should not be changed manually in the generated projects. This allows to keep the various projects aligned and have a consistent behavior when we develop on multiple projects. Sometimes a newer copier template version may be applied to a project before the others, so there is a period where there is a disalignment, but at least is a controlled one.

• typing annotations are not checked in the tests because tests do not need to be perfect and we want to be able to write them fast.