Fix shape attribute for MultiIndex

[shoyer]

This fix ensures that idx.shape == (len(idx),) if idx is a MultiIndex.

Also added tests for other ndarray compat properties.

[jreback]

hmm these should be the same
is something failing?

[shoyer]

@jreback here's what I found on master:

In [1]: import pandas as pd

In [2]: idx = pd.MultiIndex.from_arrays([['a', 'b'], [0, 1]])

In [3]: idx
Out[3]:
MultiIndex(levels=[[u'a', u'b'], [0, 1]],
           labels=[[0, 1], [0, 1]])

In [4]: idx.shape
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-f9305225184b> in <module>()
----> 1 idx.shape

/Users/shoyer/dev/pandas/pandas/core/base.pyc in shape(self)
    298     def shape(self):
    299         """ return a tuple of the shape of the underlying data """
--> 300         return self._data.shape
    301
    302     @property

AttributeError: 'NoneType' object has no attribute 'shape'

[jreback]

this is a little odd because a MultiIndex is 1-d. So this could be a bit confusing. len(idx) == shape(idx)[0]

[shoyer]

IMO MultiIndex can be unambiguously interpreted as a 1d array of tuples. I don't think it's surprising to have len(idx) == shape(idx)[0] -- that's exactly the case for any 1d numpy array. All the other indexes already have shape defined (in the same way).

[jreback]

I know but you want to return (5,20) or something right? (e.g. tuple of length of levels)?
maybe could make a new attribute? thought this prob doesn't break anything

[shoyer]

Nope, I just want to return (len(idx),)

On Fri, Oct 24, 2014 at 12:04 PM, jreback notifications@github.com
wrote:

I know but you want to return (5,20) or something right? (e.g. tuple of length of levels)?

maybe could make a new attribute? thought this prob doesn't break anything

Reply to this email directly or view it on GitHub:
#8609 (comment)

[jreback]

ahh, then this is indeed a missing component. ok, rebase and will put in

[shoyer]

rebased and green