## Question

Asked By – Yawar

I have a DataFrame with a MultiIndex created after some grouping:

```
import numpy as np
import pandas as pd
from numpy.random import randn
df = pd.DataFrame({'A' : ['a1', 'a1', 'a2', 'a3'],
'B' : ['b1', 'b2', 'b3', 'b4'],
'Vals' : randn(4)}
).groupby(['A', 'B']).sum()
# Vals
# A B
# a1 b1 -1.632460
# b2 0.596027
# a2 b3 -0.619130
# a3 b4 -0.002009
```

How do I prepend a level to the MultiIndex so that I turn it into something like:

```
# Vals
# FirstLevel A B
# Foo a1 b1 -1.632460
# b2 0.596027
# a2 b3 -0.619130
# a3 b4 -0.002009
```

**Now we will see solution for issue: Prepend a level to a pandas MultiIndex **

## Answer

A nice way to do this in one line using `pandas.concat()`

:

```
import pandas as pd
pd.concat([df], keys=['Foo'], names=['Firstlevel'])
```

An even shorter way:

```
pd.concat({'Foo': df}, names=['Firstlevel'])
```

This can be generalized to many data frames, see the docs.

This question is answered By – okartal

**This answer is collected from stackoverflow and reviewed by FixPython community admins, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 **