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numpy-gitbot opened this issue Oct 19, 2012 · 3 comments
Closed

flatten_dtype does not handle titles (Trac #1591) #2187

numpy-gitbot opened this issue Oct 19, 2012 · 3 comments
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00 - Bug component: numpy.lib
Milestone
1.6.0

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Original ticket http://projects.scipy.org/numpy/ticket/1591 on 2010-08-23 by trac user nasturtium86, assigned to unknown.

numpy.lib.io.flatten_dtype() raises "ValueError: too many values to unpack" when you run it on a dtype that has titles.

For example, this code works:

import numpy
dtype1 = numpy.dtype([("Current","f8"),("Voltage","f8"), "Power","f8")])
print numpy.lib.io.flatten_dtype(dtype1)

But this code doesn't:

import numpy
dtype2 = numpy.dtype([(("Amps","Current"),"f8"),(("Volts","Voltage"),"f8"),(("Watts","Power"),"f8")])
print numpy.lib.io.flatten_dtype(dtype2)

The following monkey patch fixes the problem:

def flatten_dtype(ndtype):
    """
    Unpack a structured data-type.

    """
    names = ndtype.names
    if names is None:
        return [ndtype]
    else:
        types = []
        for field in names:
            typ_fields = ndtype.fields[field]
            flat_dt = flatten_dtype(typ_fields[0])
            types.extend(flat_dt)
        return types
numpy.lib.io.flatten_dtype=flatten_dtype

With this monkey patch in place, both dtype1 and dtype2 are handled correctly.

There is a thread open about this issue at [http://www.mail-archive.com/numpy-discussion@scipy.org/msg27441.html]
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@pierregm wrote on 2010-09-13

  • Should be fixed in r8713. Please confirm so that I can close the ticket.

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@rgommers wrote on 2010-10-14

>>> import numpy
>>> dtype2 = numpy.dtype([(("Amps","Current"),"f8"),(("Volts","Voltage"),"f8"),(("Watts","Power"),"f8")])
>>> import numpy.lib.npyio
>>> print(numpy.lib.npyio.flatten_dtype(dtype2))
[dtype('float64'), dtype('float64'), dtype('float64')]

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Milestone changed to 1.6.0 by @mwiebe on 2011-05-24

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