A Tuesday 10 June 2008, Swank, Craig escrigué:
> Hello,
> When I make a list with list comprehensions, I get what I believe are
> incorrect results. I made a short example that shows what I'm
> talking about. I'm not sure if this is a bug in the iterator, or if
> this behavior is by design.
>
> Thanks,
>
> Craig
>
> ***************************************************
>
> import tables, random
>
> class Example(tables.IsDescription):
> col1 = tables.Int32Col(pos=1)
> col2 = tables.Int32Col(pos=2)
>
> hFile = tables.openFile('test.h5', 'w')
> table = hFile.createTable('/', 'table', Example)
> entry = table.row
>
> for i in range(40):
> entry['col1'] = random.randint(0, 5)
> entry['col2'] = random.randint(0, 5)
> entry.append()
>
> table.flush()
>
> for i in table.where('col1 == 2'):
> print i
>
> """gave:
> (2, 5)
> (2, 4)
> (2, 4)
> (2, 5)
> (2, 0)
> that is fine
> """
>
> l = [i for i in table.where('col1 == 2')]
>
> print l
>
> """gave:
> [(5, 2), (5, 2), (5, 2), (5, 2), (5, 2)]
> that is no good
> """
>
> cond = table.where('col1 == 2')
>
> l = [i for i in cond]
>
> print l
>
> """gave:
> [(5, 2), (5, 2), (5, 2), (5, 2), (5, 2)]
> that is also no good
> """
Yes, this is expected: you are referencing the row iterator, but without
specifying which value do you want to get. Use i[:] or
i.fetch_all_fields() (see the "Row methods" section of the chapter 4 of
UG) for getting what you want.
>
> print cond
>
> """ and this gave:
> (5, 2)
> this is really unexpected (for me)
> """
>
> hFile.close()
Well, this is the same case as before, because what you are printing is
a representation of the iterator itself, and not a specific value of it
(which, OTOH, makes no sense out of a loop).
Cheers,
--
Francesc Alted
Freelance developer
Tel +34-964-282-249
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