MonthOffset() gives increase of 1 day instead of 1 month

[jorisvandenbossche]

From #7375 (comment):

In [67]: from pandas.tseries import offsets

In [69]: d = pd.Timestamp('2014-01-01 09:00:00')

In [70]: d + offsets.MonthOffset()
Out[70]: Timestamp('2014-01-02 09:00:00')

In [71]: offsets.MonthOffset().apply(d)
Out[71]: Timestamp('2014-01-02 09:00:00')

In [72]: d + offsets.Day()
Out[72]: Timestamp('2014-01-02 09:00:00')

[jreback]

as noted in #7375. This (and YearOffset), need an apply implementation as they are using the DateOffset one (which is day-based). The constructor is ok.

doc-string should be expanded as well.

[hayd]

Also noticed this with #7599, confusing.

I need to fix up #6318 in 2.6 (grumble grumble), I don't recall if that addressed this... ? (maybe not...)

[jreback]

you need to specify month=1 and it will work
(it's interpreting the first arg as the day keyword)

[hayd]

Hmmm, + seems to set the month:

In [11]: pd.Timestamp.now()
Out[11]: Timestamp('2014-08-09 13:59:37.263338')

In [12]: pd.Timestamp.now() + pd.offsets.MonthOffset(month=1)
Out[12]: Timestamp('2014-01-09 13:59:39.467444')

In [13]: pd.Timestamp.now() + pd.offsets.MonthOffset(month=2)
Out[13]: Timestamp('2014-02-09 13:59:41.586575')

[jbrockmendel]

This is semi-closed by #18375. MonthOffset should never be used directly, will now raise NotImplementedError if you try the addition or apply in the OP. MonthOffset, QuarterOffset, YearOffset are base classes that should probably be privatized.

Or they could be adapted so that the base classes are non-anchored and just increment by 1, 3, and 12 months respectively.

[jreback]

@jbrockmendel ok, can you add this to the API breaking section

and add some tests that these now raise NotImplementedError (use #18375 issue).

[jbrockmendel]

Out of town for a couple days, will address then when no longer typing with thumbs

[ron819]

Any chance this will be fixed for the next release?

[mroeschke]

Looks like this has been effectively privatized. Going to close.

In [4]: In [70]: d + offsets.MonthOffset()
   ...:
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-c6cd081d9308> in <module>
----> 1 d + offsets.MonthOffset()

AttributeError: module 'pandas.tseries.offsets' has no attribute 'MonthOffset'