BUG: .loc operation cannot locate existing index when having single string as index for dataframe ('string',)

[carlonlv]

BUG: .loc operation cannot locate existing index when having single string as index for dataframe ('string',)

[carlonlv]

Thanks for the clarification. I was simply using the dataframe as dictionary. I guess this is one of the "gotcha" moment.

[carlonlv]

Note that the same operation with tuples with length >= 2 works as expected.

Also in the above example, if I do temp.loc[temp.index == ('h',), 'b'] = True, it also works fine

[mbarki-mohamed]

Please have a look at the following answer on StackOverflow; (it's an old one but still relevant)
https://stackoverflow.com/questions/40186361/pandas-dataframe-with-tuple-of-strings-as-index

It will work if you pass the tuple inside a list as argument to the loc function (explanation in the link)
temp.loc[('h',), 'b'] = True # error
to
temp.loc[[('h',)], 'b'] = True # works fine

Hope this helps !

[rhshadrach]

Thanks for the report. pandas uses tuples to signify values in a MultiIndex, and this is the reason why your lookup fails. One idea is to treat non-MulitIndexes differently here, allowing for lookups with tuples, whereas supplying tuples when the index is a MultiIndex would interpret them as levels. Perhaps this has some bad implications though, further investigations are welcome!