Closed
Description
Follow-ups for #9667. Noticed 2 methods which can return DataFrame.
1. Index.str.extract
As shown in docstring, it returns DataFrame when the expression has 2 or more groups.
pd.Series(['a1', 'b2', 'c3']).str.extract('[ab](\d)')
#0 1
#1 2
#2 NaN
# dtype: object
pd.Series(['a1', 'b2', 'c3']).str.extract('([ab])(\d)')
# 0 1
#0 a 1
#1 b 2
#2 NaN NaN
Currently, Index.str.extract raises an error in both cases. I think 1st case should return Index, and 2nd case should raise understandable error.
pd.Index(['a1', 'b2', 'c3']).str.extract('[ab](\d)')
# AttributeError: 'Index' object has no attribute 'index'
pd.Index(['a1', 'b2', 'c3']).str.extract('([ab])(\d)')
# AttributeError: 'Index' object has no attribute 'empty'
2. Index.str.get_dummies
Because it returns DataFrame, should raise an understandable error.
pd.Index(['a1', 'b2', 'c3']).str.get_dummies()
# AttributeError: 'Index' object has no attribute 'fillna'
CC: @mortada