[SPARK-10782] [Python] Update dropDuplicates documentation

[asokadiggs]

Documentation for dropDuplicates() and drop_duplicates() is one and the same. Resolved the error in the example for drop_duplicates using the same approach used for groupby and groupBy, by indicating that dropDuplicates and drop_duplicates are aliases.

[asokadiggs]

FYI - I've used spark/python/docs/make html to generate the updated HTML versions of the files and visually verified the result in the resulting documentation.

[SparkQA]

Test build #1822 has finished for PR 8930 at commit 279d620.

• This patch fails Python style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

I was going to say, I don't think this addresses the problem you identified, but then I realized there's no separate declaration of drop_duplicates? so I probably don't understand where that's coming from. If it must necessarily clone dropDuplicates docs then I agree with your note. Looks like this needs a style fix though. See the test result.

[asokadiggs]

Correct - there is no separate declaration for drop_duplicates. There is a section in dataframe.py at approximately line 1280-1285 that sets drop_duplicates = dropDuplicates and groupby = groupBy for Pandas compatibility. So there isn't an option to separately document drop_duplicates or groupby.

I implemented the same solution for drop_duplicates as is already implemented for groupby. At least for me it's readable and understandable, so it works.

I found the test result - I'll figure out the white space error and resubmit.

[davies]

LGTM

[SparkQA]

Test build #1825 has finished for PR 8930 at commit 279d620.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.