Get keys of pandas.Series.value_counts

Demo:

In [165]: s
Out[165]:
female     6700
male       6194
brand      5942
unknown    1117
Name: value_counts, dtype: int64

In [166]: s.index.tolist()
Out[166]: ['female', 'male', 'brand', 'unknown']

Plot:

In [169]: s.plot.bar(rot=0)
Out[169]: <matplotlib.axes._subplots.AxesSubplot at 0xd659da0>

Result: