BUG: Addition raises TypeError if Period is on rhs

[sinhrks]

• tests added / passed
• passes git diff upstream/master | flake8 --diff
• whatsnew entry

Period addition raises TypeError if Period is on right hand side.

1 + pd.Period('2011-01', freq='M')
# TypeError: unsupported operand type(s) for +: 'int' and 'pandas._period.Period'

Expected

1 + pd.Period('2011-01', freq='M')
# Period('2011-02', 'M')

[jreback]

didn't you make this an issue somewhere? (or maybe just a comment)

[jreback]

can use ABCPeriod

[sinhrks]

No existing issue. Updated the top comment.

[jreback]

is there a reference somewhere on this? just curious

[sinhrks]

I couldn't find as long as I searched. We can fix Timestamp if there is a workaround.

[jreback]

on what I mean is where you saw that it didn't work?

[sinhrks]

Once I tried to add __radd__ to cdef Period and found it doesn't work. Then noticed _Timestamp impl. I'm not sure where _Timestamp impl derived from.

[kawochen]

http://docs.cython.org/src/userguide/special_methods.html#arithmetic-methods

[jreback]

ahh so this means you can leave Period and we don't need _Period. That's only necessary for Timestamp for example because we are extending a c class itself
here the class is already in cython

but what it does mean is that add needs to handle reversed args directly (and similarly for other arith ops)

[sinhrks]

I read the doc something like below. This looks work removing _Period class.

   def __add__(self, other):
       if isinstance(self, Period):
           ...
       elif isinstance(other, Period):
           return other + self
       else:
           ...

[codecov-io]

Current coverage is 84.14%

Merging #13069 into master will increase coverage by +<.01%

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- Hits          42288      42265    -23   
+ Misses         7973       7966     -7   
  Partials          0          0          

1. 2 files (not in diff) in pandas/tseries were modified. more
   • Misses -4
   • Hits -22
2. 2 files (not in diff) in pandas were modified. more
   • Misses -3
   • Hits -5

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[jreback]

thanks @sinhrks