Inheriting from numpy.recarray, unicode issue

I have made a subclass of a numpy.recarray. The purpose of the class is to provide pretty printing for record arrays while maintaining the record array functionality.

Here is the code:

import numpy as np
import re

class TableView(np.recarray):

    def __new__(cls,array):
        return np.asarray(array).view(cls)

    def __str__(self):
        return self.__unicode__().encode("UTF-8")

    def __repr__(self):
        return self.__unicode__().encode("UTF-8")

    def __unicode__(self):

        options = np.get_printoptions()
        nrows = len(self)

        print "unicode called"

        if nrows > 2*options['edgeitems']:
            if nrows > options['threshold']:
                nrows = 2*options['edgeitems'] + 1

        ncols = len(self.dtype)

        fields = self.dtype.names

        strdata = np.empty((nrows + 1,ncols),dtype='S32')
        strdata[0] = fields

        np_len = np.vectorize(lambda x: len(x))
        maxcolchars = np.empty(ncols,dtype='i4')

        for i, field in enumerate(fields):
            strdata[1:,i] = re.sub('[\[\]]','',np.array_str(self[field])).split()
            maxcolchars[i] = np.amax(np_len(strdata[:,i]))

        rowformat = ' '.join(["{:>%s}" % maxchars for maxchars in maxcolchars])
        formatrow = lambda row: (rowformat).format(*row)
        strdata = np.apply_along_axis(formatrow,1,strdata)

        return '\n'.join(strdata)

Here is how it prints:

In [3]: x = np.array([(22, 2, -1000000000.0, 2000.0), (22, 2, 400.0, 2000.0),
   ...:  (22, 2, 500.0, 2000.0), (44, 2, 800.0, 4000.0), (55, 5, 900.0, 5000.0),
   ...:  (55, 5, 1000.0, 5000.0), (55, 5, 8900.0, 5000.0),
   ...:  (55, 5, 11400.0, 5000.0), (33, 3, 14500.0, 3000.0),
   ...:  (33, 3, 40550.0, 3000.0), (33, 3, 40990.0, 3000.0),
   ...:  (33, 3, 44400.01213545, 3000.0)],  
   ...:           dtype=[('subcase', '<i4'), ('id', '<i4'), ('vonmises', '<f4'), ('maxprincipal', '<f4')])

In [6]: TableView(x)
unicode called
Out[6]: 
subcase id        vonmises maxprincipal
     22  2 -1.00000000e+09        2000.
     22  2  4.00000000e+02        2000.
     22  2  5.00000000e+02        2000.
     44  2  8.00000000e+02        4000.
     55  5  9.00000000e+02        5000.
     55  5  1.00000000e+03        5000.
     55  5  8.90000000e+03        5000.
     55  5  1.14000000e+04        5000.
     33  3  1.45000000e+04        3000.
     33  3  4.05500000e+04        3000.
     33  3  4.09900000e+04        3000.
     33  3  4.44000117e+04        3000.

But this does not work when i print only one row:

In [7]: TableView(x)[0]
Out[7]: (22, 2, -1000000000.0, 2000.0)

It works for multiple rows:

In [8]: TableView(x)[0:1]
unicode called
Out[8]: 
subcase id        vonmises maxprincipal
     22  2 -1.00000000e+09        2000.

Upon further investigation:

In [10]: type(TableView(x)[0])
Out[10]: numpy.record

In [11]: type(TableView(x)[0:1])
Out[11]: __main__.TableView

How can i make a numpy.record of TableView have the same unicode?

Solution

Your diagnosis is right. A single element of this class is a record, not an Tableview array.

And indexing with a slice or list, [0:1] or [[0]], is the immediate solution.

Trying to subclass np.record and changing the elements of the Tableview seems complicated.

You might try customizing the __getitem__ method. This is called when you index the array.

It ends with:

    else:
        # return a single element
        return obj

A modified version might return a single element Tableview instead

        return Tableview([obj])

But that might produce some sort of endless recursion, keeping you from accessing elements as regular records.

Otherwise you might just want to live with the slice indexing.

Inheriting from numpy.recarray, __unicode__ issue

Inheriting from numpy.recarray, unicode issue