API/BUG: Index creation with named Index resets name

[sinhrks]

import pandas as pd
idx = pd.Index([1, 2 ,3], name='x')
pd.Index(idx)
# Int64Index([1, 2, 3], dtype='int64')

A point is whether to reset existing Index name in below case. Current impl can't distinguish whether name is not passed, or passed None explicitly.

pd.Index(idx, name=None)
# -> should reset name?

[jreback]

Same for DatetimeIndex. smells like a buggy. Should preserve meta-data in the constructor (for another passed Index)

In [18]: pd.DatetimeIndex(pd.date_range('20130101',periods=3,name='foo'))
Out[18]: DatetimeIndex(['2013-01-01', '2013-01-02', '2013-01-03'], dtype='datetime64[ns]', freq='D')

[mbirdi]

I tried to reproduce the bug and failed. Here is a link the code examples I ran on my laptop.

http://nbviewer.ipython.org/gist/mbirdi/7586ebc290bd90a73ed3

So in my examples I was able to reset the name of the index from 'x' to None.

[jreback]

@mbirdi this reproduces on master

In [58]: idx = pd.Index([1, 2 ,3], name='x')

In [59]: pd.Index(idx)
Out[59]: Int64Index([1, 2, 3], dtype='int64')

In [60]: pd.Index(idx).name

you need another index creation (e.g. with just a pd.Index)

[mbirdi]

@jreback
@sinhrks

Thanks for the feedback.

I see the question up for discussion now. I have never really had to create an index from an index. Is that a common thing to do in pandas? I am trying to picture why I would do that with the datasets I work with and I am coming up blank.

[jreback]

well if I have something that could be a list or an Index then I want to be able to wrap it and preserve meta data. The bottom line is that we want to have API consistency.

[IamGianluca]

I can work on this. I'll send a PR shortly.

[IamGianluca]

@jreback What should be the desired behaviour when the user passes None as the value for the argument name and the existing index we are passing had already a name?

idx = pd.Index([1, 2 ,3], name='x')
pd.Index(idx, name=None)
# -> should reset name?