How to add new column in pandas groupby?

Question

I have pandas groupby object

| A  | B | C |
|----|---|---|
| a1 | 3 | 4 |
| a2 | 6 | 2 |

And I want to add new column which will have average in row format

Required Output

| A  | B | C | Average |
|----|---|---|---------|
| a1 | 3 | 4 | 3.5     |
| a2 | 6 | 2 | 4       |

I tried

df.columns = df.columns.add_categories(['Average'])
df['Average'] = df.mean(axis = 1)

But this gives me

AttributeError: 'Index' object has no attribute 'add_categories'

jezrael · Accepted Answer · 2019-12-27 11:25:50Z

2

If there is no catogoricals in columns names only use mean:

df['Average'] = df.mean(axis = 1)

Or if want convert columns names to CategoricalIndex then use:

df.columns = pd.CategoricalIndex(df.columns)
df.columns = df.columns.add_categories(['Average'])
df['Average'] = df.mean(axis = 1)

answered Dec 27, 2019 at 11:25

jezrael

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