Implicit conversion to boolean in if and while statements

88888 Dihedral dihedral88888 at googlemail.com
Tue Feb 12 02:06:18 CET 2013


Rick Johnson於 2013年2月11日星期一UTC+8下午9時13分58秒寫道:
> 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:
> 
> > 
> 
> > list_ = [[ 1, 2, 3 ]]
> 
> > tuple_ = ([ 1, 2, 3 ])
> 
> > dict_ = [{ 1, 2, 3 }]
> 
> > frozendict_ = ({ 1, 2, 3 })
> 
> > set_ = [< 1, 2, 3 >]
> 
> > frozenset_ = (< 1, 2, 3 >)
> 
> 
> 
> I am vehemently against using more than one "opening seq char" and one "closing seq char". It works fine for single depth sequences, however, once you start nesting the mental focus required to parse the doubled openers/closers is headache inducing. I would accept wrapping the literal in some sort of 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 would 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 they 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! 
> 
> 
> 
> 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 used 
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. 

 








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