ops cleanup, named functions instead of lambdas

[jbrockmendel]

Lots more ops work in the pipeline, this is just the easy bits that don't need new tests.

Having reversed funcs that can be referenced will make things easier in some of the Index classmethods.

[pep8speaks]

Hello @jbrockmendel! Thanks for updating the PR.

Cheers ! There are no PEP8 issues in this Pull Request. 🍻

Comment last updated on February 03, 2018 at 00:27 Hours UTC

[codecov]

Codecov Report

Merging #19515 into master will decrease coverage by 0.1%.
The diff coverage is 84%.

@@            Coverage Diff             @@
##           master   #19515      +/-   ##
==========================================
- Coverage   91.69%   91.59%   -0.11%     
==========================================
  Files         148      150       +2     
  Lines       48561    48705     +144     
==========================================
+ Hits        44530    44612      +82     
- Misses       4031     4093      +62

Flag	Coverage Δ
#multiple	89.96% <84%> (-0.1%)	⬇️
#single	41.75% <64%> (+0.03%)	⬆️

Impacted Files	Coverage Δ
pandas/core/ops.py	95.22% <84%> (-0.52%)	⬇️
pandas/errors/__init__.py	92.3% <0%> (-7.7%)	⬇️
pandas/plotting/_converter.py	65.22% <0%> (-1.74%)	⬇️
pandas/core/arrays/categorical.py	94.74% <0%> (-1.04%)	⬇️
pandas/core/internals.py	95.05% <0%> (-0.42%)	⬇️
pandas/core/dtypes/dtypes.py	96.08% <0%> (-0.04%)	⬇️
pandas/core/arrays/__init__.py	100% <0%> (ø)	⬆️
pandas/core/arrays/base.py	56.66% <0%> (ø)
pandas/core/dtypes/base.py	47.61% <0%> (ø)
pandas/core/dtypes/common.py	95.37% <0%> (+0.05%)	⬆️
... and 1 more

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[jreback]

thanks!