does lack of type declarations make Python unsafe?

Alex Martelli aleax at
Thu Jun 19 19:12:34 CEST 2003

Aahz wrote:

> [As usual, Alex demonstrates his logorrhea right before he has to vanish
> on a long trip.  ;-)  I was unable to read the whole thing, but managed
> to get far enough to nitpick something.]

"To nitpick, nitpick squared".

> In article <pNfIa.206219$g92.4232233 at>,
> Alex Martelli  <aleax at> wrote:
>>In Python one generally identifies (just as informally) a container as
>>"an object which has a length" (using "length", perhaps a suboptimal
>>choice of wording, to mean "number of items currently contained") and
>>simultaneously express both 'c is a container' and 'that container is
>>not empty' by
>>    assert len(c)
> Hmmmm....  I would only do that for a sequence.  From my POV, classes,

I can't believe one could find ANY sensible objection to "doing that"
(checking len(c)) for a dictionary nor for a set.  Either your nitpick
is very poorly expressed (something that should be particularly carefully
avoided when nitpicking) or it just makes no sense whatsoever to me.

> class instances (even those not implementing any special methods), and
> modules all serve as containers for the purpose of determining what an
> appropriate "container object" is for any particular program.

You may indeed choose to call a class (&c) "a container", because it
does contain some things, just as some (e.g.) C programmer might choose
to call a struct "a container" for the same reason.  It's simply not
the common definition used in computer science (cfr. for example , , &c).


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