Kickstarting projects with Cookiecutter PyData Berlin - July 1, 2017 Raphael Pierzina

Thanks to the organizers for a great event!

$ whoami

Hi there! I’m Raphael

• Maintainer and core developer of Cookiecutter • Contributor to pytest and community person • Creator of the cookiecutter-pytest-plugin template • Software Engineer at moovel Group

@hackebrot

Agenda 1. What is Cookiecutter? 2. How does Cookiecutter work? 3. Create your own Cookiecutter template 4. Popular Cookiecutter templates 5. Demo: A custom Jupyter widget

1. What is Cookiecutter?

@hackebrot

@hackebrot

$ cookiecutter gh:pytest-dev/cookiecutter-pytest-plugin

full_name [Raphael Pierzina]: email [raphael@hackebrot.de]: github_username [hackebrot]: plugin_name [foobar]: emoji module_name [emoji]: short_description [A simple plugin to use with Pytest]: emoji plugin version [0.1.0]: pytest_version [3.1.1]: 3.1.2 Select docs_tool: 1 - mkdocs 2 - sphinx 3 - none Choose from 1, 2, 3 [1]: 1 Select license: 1 - MIT 2 - BSD-3 3 - GNU GPL v3.0 4 - Apache Software License 2.0 5 - Mozilla Public License 2.0 Choose from 1, 2, 3, 4, 5 [1]: 2 INFO:post_gen_project:Moving files for mkdocs. INFO:post_gen_project:Removing all temporary license files INFO:post_gen_project:Removing jinja2 macros py @hackebrot

pytest-emoji/ ├── LICENSE ├── MANIFEST.in ├── README.rst ├── appveyor.yml ├── docs │ └── index.md ├── mkdocs.yml ├── pytest_emoji.py ├── setup.py ├── tests │ ├── conftest.py │ └── test_emoji.py └── tox.ini py @hackebrot

Project • GitHub: https://github.com/audreyr/cookiecutter • Documentation: https://cookiecutter.readthedocs.io • PyPI: https://pypi.python.org/pypi/cookiecutter @hackebrot

Features • Cross-platform: Windows, Mac, and Linux are officially supported • Works with CPython 2.7, 3.3, 3.4, 3.5, 3.6 and PyPy • Project templates can be in any programming language or markup format @hackebrot

$ pip install cookiecutter

$ brew install cookiecutter

$ sudo apt-get install cookiecutter

$ conda install -c conda-forge cookiecutter

Community • Free and open source software: BSD license • 154 individual contributors from around the world • More than 1000 public templates on GitHub @hackebrot

Contributing • Development of Cookiecutter is community-driven • Connect with other Cookiecutter contributors and users on https://gitter.im/audreyr/cookiecutter • Everyone is invited to contribute! @hackebrot

2. How does Cookiecutter work?

CLI + Python API • Cookiecutter can be either used as a command- line interface app or as a Python library • Both interfaces support a number of options for controlling the level of verbosity, suppressing user prompting, providing extra context and many other things @hackebrot

$ cookiecutter [OPTIONS] TEMPLATE [EXTRA_CONTEXT] ...

$ cookiecutter -v --no-input cookiecutter-pytest-plugin license=BSD-3 docs_tool=sphinx

# -*- coding: utf-8 -*- from cookiecutter.main import cookiecutter def run_cookiecutter(): template = 'gh:pytest-dev/cookiecutter-pytest-plugin' project_dir = cookiecutter(template) print(f"Project generated in {project_dir}!") if __name__ == '__main__': run_cookiecutter() py @hackebrot

Templating with Jinja2 • Jinja2 is a modern and designer-friendly templating language for Python, modelled after Django’s templates. • It is fast, widely used and secure with the optional sandboxed template execution environment @hackebrot

# -*- coding: utf-8 -*- import pytest def pytest_addoption(parser): group = parser.getgroup('{{cookiecutter.plugin_name}}') group.addoption( ' --foo', action='store', dest='dest_foo', default='{% now "utc", "%Y" %}', help='Set the value for the fixture "bar".' ) parser.addini('HELLO', 'Dummy pytest.ini setting') py @hackebrot

{ "full_name": "Raphael Pierzina", "github_username": "hackebrot", "plugin_name": "foobar", "module_name": "{{ cookiecutter.plugin_name|lower|replace('-', '_') }}", "short_description": "A simple plugin to use with Pytest", "version": "0.1.0", "pytest_version": "3.1.1", "docs_tool": ["mkdocs", "sphinx", "none"], "license": [ "MIT", "BSD-3", "GNU GPL v3.0", "Apache Software License 2.0", "Mozilla Public License 2.0" ] } json @hackebrot

git + mercurial (+ zip) • Cookiecutter works with local templates on your filesystem or remote Git or Mercurial repositories • Short-hands for GitHub, BitBucket, and GitLab • Open Pull Request for adding support for templates from zip files or zip URLs (#961) @hackebrot

3. Create your own Cookiecutter template

Template project • Cookiecutter takes a source directory tree and copies it into your new project • It replaces all the names that it finds surrounded by templating tags {{ and }} with names that it finds in the cookiecutter.json file @hackebrot

$ mkdir hello-pydata $ cd hello-pydata $ mkdir {{cookiecutter.project_slug}} $ cd {{cookiecutter.project_slug}} @hackebrot

Cookiecutter namespace • Anything inside templating tags can be placed inside a namespace. • cookiecutter.project_slug will be looked up as project_slug in cookiecutter.json @hackebrot

$ touch {{cookiecutter.script_name}}.py @hackebrot

# -*- coding: utf-8 -*- def hello_pydata(): print('Hello PyData {{cookiecutter.location}}!') if __name__ == '__main__': hello_pydata() py @hackebrot

Context • Cookiecutter needs a context file to look up all your templates items • This file goes into our hello-pydata directory, and contains all the names we’ve used @hackebrot

$ cd .. $ touch cookiecutter.json @hackebrot

{ "project_slug": "project", "location": "World", "script_name": "hello_{{cookiecutter.location|lower}}" } json @hackebrot

hello-pydata/ ├── cookiecutter.json └── {{cookiecutter.project_slug}} └── {{cookiecutter.script_name}}.py py @hackebrot

$ cookiecutter ~/hackebrot/hello-pydata/

project_slug [project]: hello-project location [World]: Berlin script_name [hello_berlin]: py @hackebrot

hello-project/ !"" hello_berlin.py py @hackebrot

$ cd hello-project/ $ python hello_berlin.py Hello PyData Berlin!

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Jinja2 syntax • {% … %} for statements • {{ … }} for expressions to print the template output • {# … #} for comments not included in the template output @hackebrot

Jinja2 control structures • For: Loop over each item in a sequence • If: Test if a variable is defined or if it’s equal to some other value • Macros: Useful to put often used idioms into reusable functions @hackebrot

{%- from "macros/rst" import doc_title, doc_subtitle -%} {{ doc_title('pytest-' + cookiecutter.plugin_name) }} rst @hackebrot

Jinja2 control structures • Assignments: Assign values to variables • Include: Return a rendered template into the current namespace • … @hackebrot

{%- if cookiecutter.license == "MIT" -%} {%- include 'licenses/MIT' %} {%- elif cookiecutter.license == "BSD-3" -%} {%- include 'licenses/BSD-3' %} {%- elif cookiecutter.license == "GNU GPL v3.0" -%} {%- include 'licenses/GPL-3' %} {%- elif cookiecutter.license == "Apache Software License 2.0" -%} {%- include 'licenses/Apache-2' %} {%- elif cookiecutter.license == "Mozilla Public License 2.0" -%} {%- include 'licenses/MPL-2' %} {%- endif -%} txt @hackebrot

Jinja2 filters • replace: Return a copy of the value with all occurrences of a substring replaced • lower: Convert a value to lowercase • upper: Convert a value to uppercase @hackebrot

{ "full_name": "Raphael Pierzina", "github_username": "hackebrot", "plugin_name": "foobar", "module_name": "{{ cookiecutter.plugin_name|lower|replace('-', '_') }}", "short_description": "A simple plugin to use with Pytest", "version": "0.1.0", "pytest_version": "3.1.1", "docs_tool": ["mkdocs", "sphinx", "none"], "license": [ "MIT", "BSD-3", "GNU GPL v3.0", "Apache Software License 2.0", "Mozilla Public License 2.0" ] } json @hackebrot

Jinja2 filters • tojson: Dump a structure to a JSON string • sort: Sort an iterable in ascending order by default, or descending with an extra arg. Also allows to sort by an attribute @hackebrot

Jinja2 filters • select: Filter a sequence of objects by applying a test to each object • groupby: Group a sequence of objects by a common attribute @hackebrot

Jinja2 extensions • jinja2-time: Builtin into cookiecutter to insert a string representation of a datetime object • … • … @hackebrot

{#- source: http: //opensource.org/licenses/MIT #} The MIT License (MIT) Copyright (c) {% now 'utc', '%Y' %} {{cookiecutter.full_name}} Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. txt @hackebrot

4. Popular Cookiecutter templates

https://github.com/audreyr/ cookiecutter-pypackage @hackebrot

cookiecutter-pypackage • Project structure for Python packages • Testing with unittest or pytest • Tox for testing compatibility across Python versions • Sphinx for documentation @hackebrot

https://github.com/pydanny/ cookiecutter-django @hackebrot

cookiecutter-django • Template for Django 1.10 and Python 3.4 or 3.5 • Optimized development and production settings • tests with unittest or pytest and 100% test coverage • Docker support using docker-compose • Bootstrap, 12-Factor, SSL, many other features @hackebrot

https://github.com/pytest-dev/ cookiecutter-pytest-plugin @hackebrot

cookiecutter-pytest-plugin • Installable PyPI package with comprehensive README.rst file • Tests for your plugin with tox, pytest, and CI config • Example code for a fixture, a CLI option, and a pytest.ini option • Optional documentation with either Sphinx or MkDocs • Choose from several FOSS licenses @hackebrot

https://github.com/pybee/ Python-iOS-template @hackebrot

Python-iOS-template • Generates Python apps that will run under iOS • Supports Python 2.7, 3.4, and 3.5 • Works well with the toga GUI toolkit for native iOS widgets @hackebrot

5. Demo: A custom Jupyter widget

https://github.com/jupyter- widgets/widget-cookiecutter @hackebrot

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If you or your company are using Cookiecutter, please support its development! patreon.com/hackebrot @hackebrot

@hackebrot