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Adrian Price-Whelan ! adrn " adrianprw Kelle Cruz ! kelle " kellecruz

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Adrian Price-Whelan Postdoctoral fellow Princeton University (visiting CCA this year, Flatiron fellow 2019) ! adrn " adrianprw

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I’m mostly an astrophysicist (part-time software developer) I use the dynamics of stars throughout the Milky Way to study Dark Matter (see October issue of Science, “Sky Rivers”) I develop specialized software for Galactic dynamics Dominant computational costs: numerical integration + probabilistic inference (sampling)

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Adrian Price-Whelan Astropy lead developer ! adrn " adrianprw Postdoctoral fellow Princeton University (visiting CCA this year, Flatiron fellow 2019)

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How do I represent and transform astronomical coordinates in Python? 2011

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the year 2011

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the year 2011

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How do I represent and transform astronomical coordinates in Python? 2011

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astrolib astropysics coordlib ephempy kapteyn pyastro pyast + more How do I represent and transform astronomical coordinates in Python? 2011

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source: ADS

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source: ADS Python IDL Matlab Perl

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create a Python package with generic functionality that most astronomers need Idea:

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source: ADS Python IDL Matlab Perl astropy

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source: ADS Python IDL Matlab Perl astropy

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Library

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Library Community Ecosystem

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= library “The ultimate goal that we seek is a package that would contain much of the core functionality and some common tools required across Astronomy, but not everything Astronomers will ever need.”

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extending the scientific Python “stack” adapted from Jake Vanderplas

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extending the scientific Python “stack” adapted from Jake Vanderplas

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extending the scientific Python “stack” adapted from Jake Vanderplas

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extending the scientific Python “stack” adapted from Jake Vanderplas

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extending the scientific Python “stack” adapted from Jake Vanderplas

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adapted from Jake Vanderplas + many more

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Why?

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Why need a library for astronomy?

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Custom binary file formats (e.g., FITS) Why need a library for astronomy?

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Custom binary file formats (e.g., FITS) Represent units & quantities in code Why need a library for astronomy?

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Why need a library for astronomy?

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Custom binary file formats (e.g., FITS) Represent units & quantities in code Why need a library for astronomy?

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Custom binary file formats (e.g., FITS) Represent units & quantities in code Coordinate systems & transformations Why need a library for astronomy?

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Why need a library for astronomy?

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Custom binary file formats (e.g., FITS) Represent units & quantities in code Coordinate systems & transformations Commonly-used but niche statistics (not in scipy.stats) Why need a library for astronomy?

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Custom binary file formats (e.g., FITS) Represent units & quantities in code Coordinate systems & transformations Commonly-used but niche statistics (not in scipy.stats) OMG ASCII tables Why need a library for astronomy?

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Custom binary file formats (e.g., FITS) Represent units & quantities in code Coordinate systems & transformations Commonly-used but niche statistics (not in scipy.stats) OMG ASCII tables Ultra-precise timing (pulsars!) Why need a library for astronomy?

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leap seconds

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Custom binary file formats (e.g., FITS) Represent units & quantities in code Coordinate systems & transformations Commonly-used but niche statistics (not in scipy.stats) OMG ASCII tables Super-precise timing (pulsars!) Plotting images of the sky (a sphere! projections…) Why need a library for astronomy?

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What?

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Core functionality and common tools for astronomers

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Core functionality and common tools for astronomers Focus on user interface design

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Example: astronomical coordinates (α, δ, D) = (86.7∘, 53.09∘, 27 pc) (α, δ, D) = (05h46m48s, + 53d05m24s, 27 pc) (x, y, z) = (0.9, 16.2, 21.6) pc (l, b, D) = (159.14∘, 12.46∘, 27 pc) J05464800 + 5305240

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Example: astronomical coordinates Reference frame Coordinate system Coordinate representation Component formatting (α, δ, D) = (86.7∘, 53.09∘, 27 pc) (α, δ, D) = (05h46m48s, + 53d05m24s, 27 pc) (x, y, z) = (0.9, 16.2, 21.6) pc (l, b, D) = (159.14∘, 12.46∘, 27 pc) J05464800 + 5305240

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Example: astronomical coordinates (α, δ, D) = (86.7∘, 53.09∘, 27 pc) (α, δ, D) = (05h46m48s, + 53d05m24s, 27 pc) (x, y, z) = (0.9, 16.2, 21.6) pc (l, b, D) = (159.14∘, 12.46∘, 27 pc) J05464800 + 5305240

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Example: astronomical coordinates high-level interface reference frame coordinate representation

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Example: astronomical coordinates high-level interface reference frame coordinate representation

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Example: astronomical coordinates high-level interface reference frame coordinate representation

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Python + C/Cython extensions Python >= 3.5 165,595 lines of Python + 87,957 lines of tests + 48,734 lines of documentation >1,000 users ~100 downloads/day astropy — v3.0.5

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astropy docs.astropy.org

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How?

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How? Community driven development

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Making community-driven development work

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Making community-driven development work 1. Use GitHub to host code, track issues, contributions - Code review - Feature requests - Feature planning - Manage releases

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Making community-driven development work 1. Use GitHub to host code, track issues, contributions - Code review - Feature requests - Feature planning - Manage releases 2. Use continuous integration to run tests - Travis CI, CircleCI, AppVeyor - Enforce good test coverage in new code - Test on multiple architectures, dependency versions

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Making community-driven development work 1. Use GitHub to host code, track issues, contributions - Code review - Feature requests - Feature planning - Manage releases 2. Use continuous integration to run tests - Travis CI, CircleCI, AppVeyor - Enforce good test coverage in new code - Test on multiple architectures, dependency versions 3. Use readthedocs to serve documentation - Documentation generated from code with Sphinx - New contributions require documentation

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Guiding principles Open source, open development

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Open source github.com/astropy/astropy

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Open development

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Open development

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Open development

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Guiding principles Open source, open development Provide tested, documented code to users

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Software testing & continuous integration

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Software testing & continuous integration

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Documentation

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Documentation

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Documentation

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Guiding principles

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Guiding principles Open source, open development Provide tested, documented code to users

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Guiding principles Open source, open development Provide tested, documented code to users Encourage contributions from users

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Guiding principles Open source, open development Provide tested, documented code to users Encourage contributions from users Don’t re-invent tools, but minimize dependencies

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Guiding principles Open source, open development Provide tested, documented code to users Encourage contributions from users Don’t re-invent tools, but minimize dependencies Feed features and functionality back upstream

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Guiding principles Open source, open development Provide tested, documented code to users Encourage contributions from users Don’t re-invent tools, but minimize dependencies Feed features and functionality back upstream Allow & encourage extending core functionality

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Who?

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Astronomers! ~270 contributors ~20 package leads & maintainers but… Who develops the Astropy library?

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Astronomers! ~270 contributors ~20 package leads & maintainers but… Who develops the Astropy library?

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Astronomers! ~270 contributors ~20 package leads & maintainers but… Who develops the Astropy library?

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Maintainers Deputies

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Maintainers Deputies • Evaluating & merging new pull requests by sub-package • Feature development & issue tracking

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The Astropy Coordination Committee Erik Tollerud Kelle Cruz Tom Aldcroft Tom Robitaille • Overall coordination and management of the Astropy project • Evaluating new affiliated packages • Arbitrating disagreements in the core package • Managing finances for the project

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numfocus.org “…promote sustainable high-level programming languages, open code development, and reproducible scientific research”

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numfocus.org “…promote sustainable high-level programming languages, open code development, and reproducible scientific research”

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How to contribute Important to guide users to and through their first few PRs Explain expectations: code + tests + docs Coding guidelines Follow PEP8 and general style of subpackage you’re working in Avoid multiple inheritance When to include C code etc. Engaging and supporting developers docs.astropy.org/en/latest/development/codeguide.html

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Documentation guidelines Docstring styles and content (for users) Comments within code (for developers) Testing guidelines Practical issues: where to put tests, how to name them, etc. Explain concepts and expectations: unit, regression, functional (i.e. unit tests not enough, even if 100% coverage) Engaging and supporting developers docs.astropy.org/en/latest/development/docguide.html docs.astropy.org/en/latest/development/testguide.html

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Coordination meetings (Astropy project developers) Developer sprints (usually during or around other meetings) Regular telecons (deadlines are good!) Google Summer of Code (2014—present, ~30 students so far) Python in Astronomy Engaging and supporting developers

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hacking the scientific attribution system Engaging and supporting developers

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Who uses the Astropy library? LIGO (detection of gravitational waves) LIGO (neutron star merger follow-up) ALMA (first observations) + many large observatories, surveys, and regular astronomers!

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= ecosystem “A common package should not preclude any other Astronomy package from existing, because there will always be more complex and/or specialized tools required.”

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Astropy affiliated packages Domain-specific astronomy Python packages that request to be part of the Astropy community Commit to Astropy goals: improving reuse, interoperability, interface standards http://affiliated.astropy.org/

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Astropy affiliated packages Core library: General tools, long-term stable, longer release schedule Affiliated packages: Specialized tools, faster development and release cycle ~40 exist to date http://affiliated.astropy.org/

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Custom tools we use, develop, and release 4 pytest plugins (all publicly released, see here https://github.com/astropy/pytest-astropy) Sphinx extensions (see https://github.com/astropy/sphinx-automodapi) Python package template (see https://github.com/astropy/package-template) Benchmarking tool: airspeed velocity (see https://asv.readthedocs.io/en/stable/)

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Goal: simplify startup and maintenance of packaged, released Python software Sets up: documentation template (Sphinx) testing infrastructure (py.test) CI configuration setup.py script (support for Cython exts.) (Uses cookiecutter) Astropy package template https://github.com/astropy/package-template

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Custom benchmarking www.astropy.org/astropy-benchmarks

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= community “Our goal is to keep ours a positive, inclusive, successful, and growing community”

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Superset of users & developers Many entry points: - Mailing lists: users, developers - Slack - Regular telecons - New: Astropy event calendar Conferences: - Workshops - Python in Astronomy - .Astronomy What is the Astropy community?

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Engaging and supporting users

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Engaging and supporting users Documentation is not enough

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Engaging and supporting users

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Tutorials colab.research.google.com Jupyter notebooks Rendered to static HTML OR Open as live notebook with Google Colaboratory

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Many lead / maintainer roles unfilled How do we prevent burnout and support devs? User -> Contributor -> Maintainer? A significant development bottleneck is code review How can we incentivize this effort? Our goal is to enable all astronomy, not solve specific science questions How do we fund “infrastructure” software like Astropy? Challenges & the future

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Tradeoff between API stability & betterizing / updating (example: astropy.units is very general and used outside of astronomy, but is it worth the headache [to users & devs] of splitting it out?) Incentivize performance enhancements Improve educational materials Challenges & the future