Pandas: How to change titles of columns

Question

I am creating a numpy matrix (2 columns, each 10 elements). After conversion to a Pandas Dataframe I want to change the names of the columns from 0->x and 1->y. How is the solution for this?

import numpy as np
import pandas as pd

x = np.arange(10)
y = x**2

# create numpy matrix of (2 x 10) 
matrix = np.stack((x, y), axis=-1)

#conversion to Pandas
df = pd.DataFrame(matrix)

print(df)

    0   1
0   0   0
1   1   1
2   2   4
3   3   9
4   4   16
5   5   25
6   6   36
7   7   49
8   8   64
9   9   81