More random python observations from a perl programmer
nascheme at ucalgary.ca
Sat Aug 21 20:50:26 CEST 1999
I think you misunderstand the intention of my post. I am not
trying to defend Python on point. Python is not perfect. I am
trying to give some information of why things are the way they
are and am trying to help a new user of the language understand
Is it really productive to keep repeating that length one tuples
in Python are weird?
Tom Christiansen <tchrist at mox.perl.com> wrote:
> nascheme at ucalgary.ca (Neil Schemenauer) writes:
>:It is not too hard to remember what is mutable and what is not.
>I'm not sure that this maps well to the way people think, considering
>that everyone keeps telling me that it's "just something you have to
>learn and/or get used to", which means it's not intuitive at first.
>And that was my point of listing it as a gotcha.
I don't deny that this is a gotcha.
> Why can python copy sequences of chars (1-byte strings)
> s = "this stuff"
> t = s
>But as soon as you have a sequence of, oh, integers for example, you
>can't use the same set-up. Very odd.
You are still confused. Python does not copy anything
implicitly. Read my other post about this. Maybe the id()
function will help:
>>> a = 'hello'
>>> b = a
[on perl copying objects]
>Yes, with 1st-class arrays (you say lists) and hashes (you say
>dictoinaries). But not with instances, which are always by definition
>references, and suffer the same confusion. That's why base types
>are easier to use for many "accidental programmers".
What happends when you have a large array and pass it to a
function? This seems pretty inefficient. If the array is not
copied then why are they so many rules about when something is
copied and when it is not.
>:> Slices in Python must be contiguous ranges of a sequence.
>:> In Perl, there's no such restriction.
>:Use a dictionary if you want this.
>Huh? How would I use a dictionary
Sorry, I didn't read you problem close enough.
[on del as a statement]
>I *really* don't undertsand this. Why does Python have so many
>"statements" compared with C or Perl? What does this actually buy you?
>I can remove variable bindings just fine with the undef() or delete()
>functions in Perl, without needing to sacrifice an entire *statement*
>in the grammar for this! There must be something important that I'm
>not understanding here, and I'd like to.
That undef() must be an interesting function to be able to modify
the binding of its caller. You don't see a conceptual problem
with this? Can user written functions do this too?
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