Specify pandas index name in the constructor

Question

Can I specify a pandas DataFrame index name in the constructor?

Said otherwise, I would like to do the following:

df = pd.DataFrame({"a":[1,2],"b":[3,4]})
df.rename_axis(index='myindex', inplace=True)

with a single line of code (by calling only the constructor)

Ablative

Chain the rename_axis without inplace to the constructor? – Poultryman

Why not chain the two, so df = pd.DataFrame({"a":[1,2],"b":[3,4]}).rename_axis(index='myindex'). – Lytton

Answer 1

You can pass an index to the DataFrame constructor with the given name that you want.

import pandas as pd

df = pd.DataFrame({"a":[1,2],"b":[3,4]}, index=pd.Index([], name='myIndex'))
df

         a  b
myIndex
0        1  3
1        2  4

Doncaster

I am receiving an error ValueError: Shape of passed values is (2, 2), indices imply (0, 2). – Ursal

I'm getting ValueError: Length of values (2) does not match length of index (0). And for a series with existing indices, pd.Series({"a": 1, "b": 3}, index=pd.Index([], name='myIndex')), the result is empty: Series([], dtype: int64) – Camboose

Answer 2

The closest you can get is inlining the .rename_axis call:

pd.DataFrame({"a": [1, 2], "b": [3, 4]}).rename_axis('myindex')

         a  b
myindex
0        1  3
1        2  4

Camboose