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Newsgroups: comp.lang.python
Date: Mon, 11 Feb 2013 05:13:58 -0800 (PST)
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Subject: Re: Implicit conversion to boolean in if and while statements
From: Rick Johnson <rantingrickjohnson@gmail.com>
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On Monday, February 11, 2013 6:40:23 AM UTC-6, Chris Angelico wrote:
> [...]
> Or doing what you were pointing and laughing at Pike for, and using
> two-symbol delimiters. You could even make it majorly logical:
>=20
> list_ =3D [[ 1, 2, 3 ]]
> tuple_ =3D ([ 1, 2, 3 ])
> dict_ =3D [{ 1, 2, 3 }]
> frozendict_ =3D ({ 1, 2, 3 })
> set_ =3D [< 1, 2, 3 >]
> frozenset_ =3D (< 1, 2, 3 >)

I am vehemently against using more than one "opening seq char" and one "clo=
sing seq char". It works fine for single depth sequences, however, once you=
 start nesting the mental focus required to parse the doubled openers/close=
rs is headache inducing. I would accept wrapping the literal in some sort o=
f declaration though, something like i proposed earlier in the thread. The =
easiest is to use:

  set({1,2,3})

but that looks like a function call! So we'd need a unique syntax. Either a=
 single tag like:

  set{1,2,3}

Or we could use start and end tags like:

  set{1,2,3}set

where "set{" and "}set" are delimiters. For lists, tuples, and dict we woul=
d use the short form because these literals are far too ubiquitous:

  [1,2,3] # list
  {k:v} # dict
  (1,2,3) # tuple

However, the grouping chars for tuples has always been confusing because th=
ey can clash with grouping of expressions. What is this?

  (1)

It's NOT a tuple! But it looks like a tuple! What is this:

  1,2

it IS a tuple, but it does not look like a tuple!=20

That's an unfortunate side effect of a poorly thought-out tuple syntax.=20