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Re: Chanelling Guido - dict subclasses

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From Peter Otten <__peter__@web.de>
Subject Re: Chanelling Guido - dict subclasses
Date Wed, 15 Jan 2014 09:40:33 +0100
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Steven D'Aprano wrote:

> In the midst of that discussion, Guido van Rossum made a comment about
> subclassing dicts:
> 
>     [quote]

>     Personally I wouldn't add any words suggesting or referring
>     to the option of creation another class for this purpose. You
>     wouldn't recommend subclassing dict for constraining the
>     types of keys or values, would you?
>     [end quote]

> This surprises me, and rather than bother Python-Dev (where it will
> likely be lost in the noise, and certain will be off-topic), I'm hoping
> there may be someone here who is willing to attempt to channel GvR. I
> would have thought that subclassing dict for the purpose of constraining
> the type of keys or values would be precisely an excellent use of
> subclassing.
> 
> 
> class TextOnlyDict(dict):
>     def __setitem__(self, key, value):
>         if not isinstance(key, str):
>             raise TypeError

Personally I feel dirty whenever I write Python code that defeats duck-
typing -- so I would not /recommend/ any isinstance() check.
I realize that this is not an argument...

PS: I tried to read GvR's remark in context, but failed. It's about time to 
to revolt and temporarily install the FLUFL as our leader, long enough to 
revoke Guido's top-posting license, but not long enough to reintroduce the 
<> operator...

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Thread

Chanelling Guido - dict subclasses Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-01-15 01:27 +0000
  Re: Chanelling Guido - dict subclasses Ned Batchelder <ned@nedbatchelder.com> - 2014-01-14 21:04 -0500
  Re: Chanelling Guido - dict subclasses Terry Reedy <tjreedy@udel.edu> - 2014-01-14 22:48 -0500
  Re: Chanelling Guido - dict subclasses F <f@hop2it.be> - 2014-01-15 07:00 +0000
  Re: Chanelling Guido - dict subclasses Peter Otten <__peter__@web.de> - 2014-01-15 09:40 +0100
    Re: Chanelling Guido - dict subclasses John Ladasky <john_ladasky@sbcglobal.net> - 2014-01-15 08:51 -0800
      Re: Chanelling Guido - dict subclasses Peter Otten <__peter__@web.de> - 2014-01-15 19:35 +0100
      Re: Chanelling Guido - dict subclasses Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-01-15 22:30 -0800
  Re: Chanelling Guido - dict subclasses Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-15 09:10 +0000
  Re: Chanelling Guido - dict subclasses Tim Chase <python.list@tim.thechases.com> - 2014-01-15 05:03 -0600
  Re: Chanelling Guido - dict subclasses Daniel da Silva <var.mail.daniel@gmail.com> - 2014-01-15 19:50 -0500
    Re: Chanelling Guido - dict subclasses Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-01-16 17:17 +1300

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