Permission or Forgiveness?

Location: D135 Level: Intermediate
Average rating: ***..
(3.88, 8 ratings)

I’ll start by introducing the motto “It’s easier to ask forgiveness than permission” and the woman who used it, Rear Admiral Grace Murray Hopper, also known as the “mother of Cobol” and the author of the first ever programming-language compiler.

I then move on to the Python context, where the motto supports the proper usage of exception-catching rather than preliminary checks; and the “rule that proves the exception” introduced by abstract base classes.

Expanding the subject, I show how “optimistic concurrency” applies that motto (while locking would “ask permission”, in essence, software transactional memory “asks forgiveness”), and how collision-detection focused networking protocols have similarly triumphed over more highly structured, “ask permission” ones like token-ring.

Moving to the fuzzier context of real life, I then show how this daring action-centric approach does not work quite as well as in the technical realm — except when applied correctly, in the right circumstances… and I try to evince a general law describing what the right circumstances for its application are, comparing and contrasting with the similar issue of “do it right the first time” versus “launch and iterate” (and the latter’s cognate “fail, but fail fast” principle).

Photo of Alex Martelli

Alex Martelli


Alex Martelli wrote “Python in a Nutshell” and co-edited
“Python Cookbook”. He’s a PSF member, and won the 2002 Activators’ Choice Award and the 2006 Frank Willison Award for contributions to the Python community. He works as Senior Staff Engineer for Google. You can read some PDFs and
watch some videos of his past presentations.

Photo of Anna Ravenscroft

Anna Ravenscroft


Anna Martelli Ravenscroft has a background in training and mentoring. Her focus is on practical, real-world problem solving and the benefits of diversity and accessibility. Anna graduated in 2010 from Stanford University with a degree in Cognitive Science. She is a member of the Python Software Foundation, a program committee member for several open source conferences, winner of the 2013 Frank Willison Award, and co-edited the Python Cookbook 2nd edition. She has spoken at PyCon, EuroPython, OSCON, and several regional Python conferences.

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Magnus Runesson
07/23/2012 4:41pm PDT

It makes you think…

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Anna Ravenscroft
07/18/2012 10:27am PDT

PDF is available at:

Picture of Anna Ravenscroft
Anna Ravenscroft
07/18/2012 10:23am PDT

Slides will be available shortly. Thanks for asking.

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Jon Guidry
07/18/2012 8:12am PDT

Hi there – will you be posting a link to slides on here? Thanks!


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