tuples, index method, Python's design

Paul Boddie paul at boddie.org.uk
Tue Apr 10 16:27:11 CEST 2007


On 10 Apr, 15:57, Steve Holden <s... at holdenweb.com> wrote:
>
> The point I am trying to make is that circumstances alter cases, and that we
> can't always rely on our intuition to determine how specific methods
> work, let alone whether they are available.

But it's telling that by adopting precisely the implementation that we
currently have for lists, we can have a tuple method which does what
most people would reasonably expect. "Why are we suddenly getting
single characters instead of whole strings?" people have presumably
exclaimed often enough, illustrating that the sequence nature of
strings is a controversial topic. Lists and tuples, however, don't
have such controversial baggage.

> I hear the screams of "just add the index() method to tuples and have
> done with it" and, to an extent, can sympathize with them. But that way
> lies creeping featurism and the next thing you know we'll have a ternary
> operator in the language - oh wait, we do now!

Yes, but the cost of adding index to tuples is minimal, and the mental
cost to programmers is arguably negative. Meanwhile, we now have to
put up with the syntactic bodge that is the ternary operator until the
time comes when it gets deprecated as something that didn't work out
or wasn't really necessary (in Python 4000, perhaps), meaning that we
now have to read third-party code more carefully, the people writing
editors and tools have to change their lexers/parsers again, and so
on.

Paul




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