[Python-Dev] enum discussion: can someone please summarize open issues? (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Sat May 4 08:46:35 CEST 2013

Guido van Rossum wrote:

Code that wants to validate a string the user typed as input. Web forms just don't work that way.

Maybe "validation" was a misleading term to use. To be more precise, I'm talking about taking input to the program (it needn't come directly from a user, it could be read from a file or database) that is supposed to be the name of a Color, and turning it into a Color instance.

For that purpose, it's convenient to have a function with only two possible outcomes: it either returns a Color instance, or raises a ValueError.

The point is that you shouldn't have to perform a separate validation step. You should be able to use EAFP -- go ahead and perform the conversion, but be prepared to catch a ValueError at some level and report it to the user.

-- Greg

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