[Numpy-discussion] loadtxt/savetxt tickets

Charles R Harris charlesr.harris at gmail.com
Mon Apr 4 12:20:33 EDT 2011


On Mon, Apr 4, 2011 at 9:59 AM, Bruce Southey <bsouthey at gmail.com> wrote:

> On 03/31/2011 12:02 PM, Derek Homeier wrote:
> > On 31 Mar 2011, at 17:03, Bruce Southey wrote:
> >
> >> This is an invalid ticket because the docstring clearly states that in
> >> 3 different, yet critical places, that missing values are not handled
> >> here:
> >>
> >> "Each row in the text file must have the same number of values."
> >> "genfromtxt : Load data with missing values handled as specified."
> >> "   This function aims to be a fast reader for simply formatted
> >> files.  The
> >>     `genfromtxt` function provides more sophisticated handling of,
> >> e.g.,
> >>     lines with missing values."
> >>
> >> Really I am trying to separate the usage of loadtxt and genfromtxt to
> >> avoid unnecessary duplication and confusion. Part of this is
> >> historical because loadtxt was added in 2007 and genfromtxt was added
> >> in 2009. So really certain features of loadtxt have been  'kept' for
> >> backwards compatibility purposes yet these features can be 'abused' to
> >> handle missing data. But I really consider that any missing values
> >> should cause loadtxt to fail.
> >>
> > OK, I was not aware of the design issues of loadtxt vs. genfromtxt -
> > you could probably say also for historical reasons since I have not
> > used genfromtxt much so far.
> > Anyway the docstring statement "Converters can also be used to
> >           provide a default value for missing data:"
> > then appears quite misleading, or an invitation to abuse, if you will.
> > This should better be removed from the documentation then, or users
> > explicitly discouraged from using converters instead of genfromtxt
> > (I don't see how you could completely prevent using converters in
> > this way).
> >
> >> The patch is incorrect because it should not include a space in the
> >> split() as indicated in the comment by the original reporter. Of
> > The split('\r\n') alone caused test_dtype_with_object(self) to fail,
> > probably
> > because it relies on stripping the blanks. But maybe the test is ill-
> > formed?
> >
> >> course a corrected patch alone still is not sufficient to address the
> >> problem without the user providing the correct converter. Also you
> >> start to run into problems with multiple delimiters (such as one space
> >> versus two spaces) so you start down the path to add all the features
> >> that duplicate genfromtxt.
> > Given that genfromtxt provides that functionality more conveniently,
> > I agree again users should be encouraged to use this instead of
> > converters.
> > But the actual tab-problem causes in fact an issue not related to
> > missing
> > values at all (well, depending on what you call a missing value).
> > I am describing an example on the ticket.
> >
> > Cheers,
> >                                       Derek
> >
> > _______________________________________________
> > NumPy-Discussion mailing list
> > NumPy-Discussion at scipy.org
> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
> Okay I see that 1071 got closed which I am fine with.
>
> I think that your following example should be a test because the two
> spaces should not be removed with a tab delimiter:
> np.loadtxt(StringIO("aa\tbb\n \t \ncc\t"), delimiter='\t',
> dtype=np.dtype([('label', 'S4'), ('comment', 'S4')]))
>
>
Make a test and we'll put it in.

Chuck
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