Software Sustainability? Lessons from IPython

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Software Sustainability? Lessons from IPython Fernando Perez (@fperez_org) UC Berkeley

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Facets of Sustainability ● Trust ● Value ● Scope ● Resources ● Need

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First, briefly, who am I? ● Physics PhD, 2002. – Lattice QCD (numerical particle physics) – IPython: Procrastinate on dissertation writing. ● Applied Mathematics Postdoc – New class of Numerical algorithms for PDEs – targeting quantum chemistry – All Python outsides, Fortran/C/C++/Cython core. ● Research Scientist “in neuroscience” ● “Member” of the SciPy community since 2001.

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Second, some quick stats/history ● IPython 0.0.1: https://gist.github.com/fperez/1579699 – 259 lines (including whitespace/comments) ● Truly an “afternoon hack”. ● My very first Python program. – It will likely be my last... But it solved a problem I had

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In a Nutshell, IPython... ● has had 16,569 commits made by 368 contributors – representing 87,837 lines of code ● is mostly written in Python, – with a well-commented source code ● has a well established, mature codebase, – maintained by a very large development team – with increasing Y-O-Y commits ● took an estimated 22 years of effort (COCOMO model) Stats: http://www.ohloh.net/p/ipython

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Trust

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Trust ● Clarity vs Transparency. ● Clarity of Governance. ● Private things in IPython: – Security list. Anyone who wants is invited. – Fiscal oversight for Numfocus. Needed for IRS compliance. – Rare private discussions, like Jupyter renaming. – Deliberately no private list: make secrecy hard by design.

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Trust Learn to let go! (The project is more important than you)

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Review, but give others the benefit of the doubt... (avoid death by a thousand nitpicks)

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Small mistakes are better than scoring points

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Disagreement, conflict, confrontation.

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Occam's razor of communities: Assume malice only when all other alternatives have been disproved.

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Value

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Value ● Always solve someone's problem. ● “Don't break userspace” - Linus Torvalds.

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Scope

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Scope ● Defining scope is a compass. ● Helps you know what to do. Helps you know what NOT TO DO.

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Resources

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Resources ● People – Volunteers – Permanent – Not just coders! ● Institutional – Universities/institutes/companies – Numfocus, PSF, etc ● $$$ – Government – Private foundations – Industry