BUG: Fix Empty DataFrame.style.render raises IndexError

[sandipchatterjee]

Fix attempt for Issue #15953

Handles DataFrames and Series with no rows or columns
using pd.DataFrame().empty or pd.Series().empty

In [1]: import pandas as pd

In [2]: pd.DataFrame().style.render()
Out[2]: '\n        <style  type="text/css" >\n        \n        \n        </style>\n\n        <table id="T_de3b3e8c_1e30_11e7_9abb_a8667f1b25b4" None>\n        \n\n        <thead>\n            \n        </thead>\n        <tbody>\n            \n        </tbody>\n        </table>\n        '

• closes BUG: Empty DataFrame.style.render raises IndexError #15953
• tests added / passed
• passes git diff upstream/master --name-only -- '*.py' | flake8 --diff
• whatsnew entry

[TomAugspurger]

Thanks! One comment on the fix. Could you also add tests and a release note in doc/source/whatsnew/v0.20.0.txt?

[TomAugspurger]

I think you'll have to change this around a bit. DataFrame.empty is True if either the index or columns is empty. So you get

pd.DataFrame([], index=[1, 2]).empty  #  True
pd.DataFrame([], columns=['A', 'B']).empty  # True

[TomAugspurger]

I think our desired output is the same as the notebook

[codecov]

Codecov Report

Merging #15971 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #15971      +/-   ##
==========================================
+ Coverage      91%   91.01%   +<.01%     
==========================================
  Files         145      145              
  Lines       49581    49581              
==========================================
+ Hits        45122    45124       +2     
+ Misses       4459     4457       -2

Flag	Coverage Δ
#multiple	88.77% <100%> (ø)	⬆️
#single	40.57% <0%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/formats/style.py	96.17% <100%> (ø)	⬆️
pandas/util/testing.py	81.13% <0%> (+0.18%)	⬆️

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[jreback]

pls rebase / update according to the comments. Needs a tests.

[TomAugspurger]

whatsnew notes should go in whatsnew/0.20.2.txt now.

[TomAugspurger]

Looks like #16441 fixed this in the meantime. Thanks anyways @sandipchatterjee, sorry about the duplicated effort.