在 Python Pandas MultiIndex 中重命名名称

Question

I try to rename a column name in a Pandas MultiIndex but it doesn't work. Here you can see my series object. Btw, why is the dataframe df_injury_record becoming a series object in this function?

Frequency_BodyPart = df_injury_record.groupby(["Surface","BodyPart"]).size()

In the next line you will see my try to rename the column.

Frequency_BodyPart.rename_axis(index={'Surface': 'Class'})

But after this, the column has still the same name.

Regards

Answer 1

One possible problem should be pandas version under 0.24 or you forget assign back like mentioned @anky_91:

df_injury_record = pd.DataFrame({'Surface':list('aaaabbbbddd'),
                                 'BodyPart':list('abbbbdaaadd')})

Frequency_BodyPart = df_injury_record.groupby(["Surface","BodyPart"]).size()
print (Frequency_BodyPart)
Surface  BodyPart
a        a           1
         b           3
b        a           2
         b           1
         d           1
d        a           1
         d           2
dtype: int64

Frequency_BodyPart = Frequency_BodyPart.rename_axis(index={'Surface': 'Class'})
print (Frequency_BodyPart)
Class  BodyPart
a      a           1
       b           3
b      a           2
       b           1
       d           1
d      a           1
       d           2
dtype: int64

If want 3 columns DataFrame working also for oldier pandas versions:

df = Frequency_BodyPart.reset_index(name='count').rename(columns={'Surface': 'Class'})
print (df)
  Class BodyPart  count
0     a        a      1
1     a        b      3
2     b        a      2
3     b        b      1
4     b        d      1
5     d        a      1
6     d        d      2