pandas bug: Series become empty somehow.

gistfile1.py

import pandas

class AggregatedValue(object):

    def __init__(self, aggfunc, value=None, original=None):
        self.aggfunc = aggfunc
        self.value = value
        self.original = original

    def __repr__(self):
        return '<AggVal: %r>' % self.value

    def __call__(self, series):
        value = self.aggfunc(series)
        return self.__class__(self.aggfunc, value=value, original=series)


class AggregatedValueConvertSeriesToList(AggregatedValue):
    def __call__(self, series):
        series = list(series)
        return super(AggregatedValueConvertSeriesToList, self).__call__(series)


idx = range(5)

d = {'date' : pandas.Series(('2011', '2011', '2011', '2012', '2013'), index=idx),
     'manager' : pandas.Series(['m1', 'm2', 'm3', 'm1', 'm2'], index=idx),
     'value' : pandas.Series([1, 1, 1, 2, 1], index=idx)}

df = pandas.DataFrame(d)


# The lengths of the original series here is 0 - it gets truncated.
result = df.pivot_table(
    rows='date', cols='manager', values='value', aggfunc=AggregatedValue(len),
    margins=False)
print 'Lengths of "originals"'
for value in result['m1']:
    print len(getattr(value, 'original', []))

# The lengths of the original series here is not 0 any more, cause we converted it to list.
result = df.pivot_table(rows='date', cols='manager', values='value',
                        aggfunc=AggregatedValueConvertSeriesToList(len),
                        margins=False)
print 'Lengths of "originals", if series was converted to lists'
for value in result['m1']:
    print len(getattr(value, 'original', []))

This outputs:

Lengths of "originals"
0 # Here, it should be 1
0 # Here, it should be 1
0
Lengths of "originals", if series was converted to lists
1
1
0