[Python-Dev] pprint(iterator)

[Guido van Rossum]

My only thought is that whatever you do, target Python 3.1, not 3.0.1.

On Tue, Jan 27, 2009 at 1:46 PM, Raymond Hettinger <python at rcn.com> wrote:
> It is becoming the norm in 3.x for functions to return iterators,
> generators, or views whereever possible.
>
> I had a thought that pprint() ought to be taught to print iterators:
>
>   pprint(enumerate(seq))
>   pprint(map(somefunc, somedata))
>   pprint(permutations(elements))
>   pprint(mydict.items())
>
> Currently, all four of those will print something like:
>
>   >>> pprint(d.items())
>   <dict_items object at 0x00FA4470>
>   >>> pprint(enumerate(d))
>   <enumerate object at 0x00FC2878>
>
> If pprint() is to give a more useful result, the question is how best to
> represent the iterators.
>
> In the examples for itertools, I adopted the convention of displaying
>  results
> like a collection with no commas or enclosing delimiters:
>
>   # chain('ABC', 'DEF') --> A B C D E F
>
> The equivalent for pprint would be the same for items, using space for items
> on one row or using linefeeds for output too long for one row.
>
> Another idea is to make-up an angle-bracket style to provide a visual cue
> for iterator output:
>
>   <'A' 'B' 'C' 'D' 'E' 'F'>
>
> Perhaps with commas:
>
>   <'A', 'B', 'C', 'D', 'E', 'F'>
>
> None of those ideas can be run through eval, nor do they identify the type
> of iterator.  Perhaps these would be better:
>
>   <enumerate object: 'A', 'B', 'C', 'D', 'E', 'F'>
>
> or
>
>  iter(['A', 'B', 'C', 'D', 'E', 'F'])
>
>
> Do you guys have any thoughts on the subject?
>
>
> Raymond
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--Guido van Rossum (home page: http://www.python.org/~guido/)