[Python-Dev] Adding NewType() to PEP 484 (original) (raw)

Steven D'Aprano steve at pearwood.info
Sat May 28 08:24:45 EDT 2016

On Fri, May 27, 2016 at 09:26:29PM -0700, Guido van Rossum wrote:

We discussed this over dinner at PyCon, some ideas we came up with:

- Dependent types, harking back to a similar concept in Ada (https://en.wikibooks.org/wiki/AdaProgramming/TypeSystem#Derivedtypes) which in that language is also spelled with "new".

I started to explain this to my non-programmer wife, I got as far as explaining types, and that we need a name for this thing, and she stopped me and said

"Please don't tell me this is leading to TypyMcTypeCheck."

[...]

- BoatyMcBoatType

The nice thing about "distinguished" is that it's a relatively rare word so it is easy to remember or look up.

I would have thought that being rare, it would be harder to remember.

Personally I'm still in favor of Derived type (but I'm more into ancient programming languages than most folks here). I could also live with Distinguished Type.

I think Derived Type is the nicest of the options. It accurately describes what it is: a type derived from another. And its shorter and easy to both say and write than "Distinguished type" (which sounds like "distinguished gentlemen" -- is it wearing a monocle and a top hat?).

"Distinguished" is too vague for my tastes, it might as well be "flibblegubble type". All types are distinguished, the type checker has to distinguish int from float from list from str, so to call NewType("userid", int) a "distinguished type" is only to call it a type.

-- Steve

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