ENH Assert_frame_equal check_names to True

[hayd]

This is a follow up to #2962, where I added a check_names=False argument to assert_frame_equal, this defaults it to True. That is, when asserting two DataFrames are equal, it compares .columns.names and .index.names, unless explicitly passing check_names=False.

I've added in check_names=False where it wouldn't make sense to check names. I've added a TODO comment (and check_names=False) where I think it probably should work but isn't... This was in the following cases:

to_csv
reindex
reset_index
groupy-a-get
pop
join (dataframe to a series)
from_xls (when setting index as first column)

i.e. these appear to drop column names (df.columns.names). Whether this behaviour is correct / desired in these cases, I'm not sure, but here they all are. :)

Note: By changing the A1 cells to 'index', I had all but one test (labelled "read xls ignores index name ?") in test_excel.py working locally (with check_names=True) , however Travis was less convinced throwing:

InvalidFileException: "There is no item named 'xl/theme/theme1.xml' in the archive"

so I reverted to the previous xls and xlsx, and added back in check_names=False. I suspect LibreOffice wasn't saving it properly...?

[hayd]

@wesm @changhiskhan @jreback Do you think this is ok to merge in?

I'm being a bit wary of changing the behaviour of assert_frame_equals if you're not onboard. (Since, it could lead to test passes merging into test fails, if assert_frame_equals is used in a test to frames with distinct column/index names.)

[jreback]

any tests failing?

[hayd]

@jreback Nope it's "good to merge"..

[jreback]

@hayd so you basically set check_names=False with a comment to check it.....

I guess maybe make a new issue refing this one....so you (or someone) can follow up in those cases.....they seem like the should work.....

[hayd]

The original PR #2962 does just that (sets it to False), this second one sets it True...

I had to go in and fixed those calls to assert_frame_equals where it wasn't working, either by setting check_names=False, changing the name (of an expected/result) or flagging it with TODO (and setting check_names=False) if I thought it could be a bug.

Then I (or someone) can then follow them up :)

[wesm]

This looks fine to merge to me. I think it'll help catch bugs

[hayd]

Sorry about that, I've a line in release notes in the PR above.