Let's use 'kser' rather than 'ks' or 's' as variable name for Series

[itholic]

Since the ks is used as koalas' import naming convention we recommended like from databricks.koalas as ks

Let's don't use ks as variable name for Series, use kser instead for unity & readability of our codes and to avoid confusing.

Plus, i think maybe we better also avoid using of just s as possible for more readability.

[itholic]

@ueshin @HyukjinKwon Could you please let me know your opinion after confirm this PR when you guys available? 😄

[codecov-io]

Codecov Report

Merging #1052 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1052   +/-   ##
=======================================
  Coverage   95.13%   95.13%           
=======================================
  Files          34       34           
  Lines        6765     6765           
=======================================
  Hits         6436     6436           
  Misses        329      329

Impacted Files	Coverage Δ
databricks/koalas/indexing.py	94.89% <100%> (ø)	⬆️
databricks/koalas/generic.py	95.73% <100%> (ø)	⬆️
databricks/koalas/groupby.py	91.39% <100%> (ø)	⬆️
databricks/koalas/window.py	97.1% <100%> (ø)	⬆️
databricks/koalas/frame.py	96.56% <100%> (ø)	⬆️

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[ueshin]

Shall we fix some more?

• frame.py: There are two for name, ks in kdf.iteritems():
• test_dataframe.py: There are some right_ks.

[ueshin]

Otherwise, LGTM.

[HyukjinKwon]

+1. Looks good except Takuya's comments too.

[itholic]

@ueshin, @HyukjinKwon Thanks for the comment! i just fix the missing ones.

[ueshin]

Shall we fix too?

test_dataframe.py: There are some right_ks.

[itholic]

@ueshin Thanks for finding! :)

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• Co-change Alert: You modified test_frame_plot.py. Often plot.py (databricks/koalas) is modified at the same time.

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[HyukjinKwon]

Merged to master.