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Newsgroups: comp.lang.python
Date: Mon, 11 Feb 2013 17:06:18 -0800 (PST)
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Subject: Re: Implicit conversion to boolean in if and while statements
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Xref: csiph.com comp.lang.python:38713

Rick Johnson=E6=96=BC 2013=E5=B9=B42=E6=9C=8811=E6=97=A5=E6=98=9F=E6=9C=9F=
=E4=B8=80UTC+8=E4=B8=8B=E5=8D=889=E6=99=8213=E5=88=8658=E7=A7=92=E5=AF=AB=
=E9=81=93=EF=BC=9A
> On Monday, February 11, 2013 6:40:23 AM UTC-6, Chris Angelico wrote:
>=20
> > [...]
>=20
> > Or doing what you were pointing and laughing at Pike for, and using
>=20
> > two-symbol delimiters. You could even make it majorly logical:
>=20
> >=20
>=20
> > list_ =3D [[ 1, 2, 3 ]]
>=20
> > tuple_ =3D ([ 1, 2, 3 ])
>=20
> > dict_ =3D [{ 1, 2, 3 }]
>=20
> > frozendict_ =3D ({ 1, 2, 3 })
>=20
> > set_ =3D [< 1, 2, 3 >]
>=20
> > frozenset_ =3D (< 1, 2, 3 >)
>=20
>=20
>=20
> I am vehemently against using more than one "opening seq char" and one "c=
losing seq char". It works fine for single depth sequences, however, once y=
ou start nesting the mental focus required to parse the doubled openers/clo=
sers is headache inducing. I would accept wrapping the literal in some sort=
 of declaration though, something like i proposed earlier in the thread. Th=
e easiest is to use:
>=20
>=20
>=20
>   set({1,2,3})
>=20
>=20
>=20
> but that looks like a function call! So we'd need a unique syntax. Either=
 a single tag like:
>=20
>=20
>=20
>   set{1,2,3}
>=20
>=20
>=20
> Or we could use start and end tags like:
>=20
>=20
>=20
>   set{1,2,3}set
>=20
>=20
>=20
> where "set{" and "}set" are delimiters. For lists, tuples, and dict we wo=
uld use the short form because these literals are far too ubiquitous:
>=20
>=20
>=20
>   [1,2,3] # list
>=20
>   {k:v} # dict
>=20
>   (1,2,3) # tuple
>=20
>=20
>=20
> However, the grouping chars for tuples has always been confusing because =
they can clash with grouping of expressions. What is this?
>=20
>=20
>=20
>   (1)
>=20
>=20
>=20
> It's NOT a tuple! But it looks like a tuple! What is this:
>=20
>=20
>=20
>   1,2
>=20
>=20
>=20
> it IS a tuple, but it does not look like a tuple!=20
>=20
>=20
>=20
> That's an unfortunate side effect of a poorly thought-out tuple syntax.

I am thinking a mutated list temporarily is useful when a list is to be use=
d=20
to be iterated through all of its elements efficiently.

A permanently mutated list is a tuple of constant objects.

As for the set type, I prefer to use the operations of the list,
dictionaries in Python to act for the designed purposes.=20

=20