BUG: Series(extension array) + extension array values addition cause runtime exception

[peterpanmj]

Code Sample, a copy-pastable example if possible

In [41]: s
Out[41]:
0    1
1    2
2    3
dtype: Int64

In [42]: s.values
Out[42]: IntegerArray([1, 2, 3], dtype='Int64')

In [43]: s + s.values
---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
<ipython-input-43-c3f015376225> in <module>()
----> 1 s + s.values

C:\Users\Public\pandas-peter\pandas\core\ops.py in wrapper(left, right)
   1231                 (is_extension_array_dtype(right) and not is_scalar(right
))):
   1232             # GH#22378 disallow scalar to exclude e.g. "category", "Int6
4"
-> 1233             return dispatch_to_extension_op(op, left, right)
   1234
   1235         elif is_datetime64_dtype(left) or is_datetime64tz_dtype(left):

C:\Users\Public\pandas-peter\pandas\core\ops.py in dispatch_to_extension_op(op,
left, right)
   1152             new_right = list(new_right)
   1153         elif is_extension_array_dtype(right) and type(left) != type(righ
t):
-> 1154             new_right = list(new_right)
   1155         else:
   1156             new_right = right

UnboundLocalError: local variable 'new_right' referenced before assignment

Problem description

Extension array add itself cause problems

Expected Output

In [2]: s + s.values
Out[2]:
0 2
1 4
2 6
dtype: Int64

Output of pd.show_versions()

INSTALLED VERSIONS ------------------ commit: 2be2ba5 python: 3.6.4.final.0 python-bits: 64 OS: Windows OS-release: 7 machine: AMD64 processor: Intel64 Family 6 Model 60 Stepping 3, GenuineIntel byteorder: little LC_ALL: None LANG: zh_CN.UTF-8 LOCALE: None.None

pandas: 0.24.0.dev0+506.g2be2ba570
pytest: 3.7.1
pip: 9.0.1
setuptools: 38.4.0
Cython: 0.28.4
numpy: 1.14.0
scipy: 1.0.0
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: 1.6.7
patsy: 0.5.0
dateutil: 2.6.1
pytz: 2017.3
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.4
feather: None
matplotlib: 2.1.2
openpyxl: 2.4.10
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.2
lxml: 4.1.1
bs4: 4.6.0
html5lib: 1.0.1
sqlalchemy: 1.2.1
pymysql: 0.7.11.None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None

[jorisvandenbossche]

Thanks for the report. Yes, this is a know bug (#22325 (comment)), and fixed along the way in that linked PR.
But given that will probably still take some time to get fixed, seems fine to already fix just that with your PR.

[jorisvandenbossche]

BTW, it is not because it are the values of itself, but a problem of series + array in general