Change pandas DataFrame columns from int to string?

I would like to change a specific(using numeric index to choose the column) column name in a pandas dataframe from integer to a string.

But it gives me back: "ValueError: invalid literal for int() with base 10: ‘col2’"

import pandas as pd
import numpy as np

arr1=[]

header = ['NA']*6
header[0] = "NAME1"
header = pd.DataFrame(header).transpose()
arr1 = pd.DataFrame(np.arange(36).reshape(6,6))
m1 = pd.concat([header,arr1])
m1.reset_index(drop=True)
print(m1.shape)
print(m1)


##renaming columns:
m1.columns.values[0] = "col2"

How can I do this? thanks

>Solution :

Use rename:

m1 = m1.rename(columns={0: 'col2'})
print(m1)

# Output
    col2   1   2   3   4   5
0  NAME1  NA  NA  NA  NA  NA
0      0   1   2   3   4   5
1      6   7   8   9  10  11
2     12  13  14  15  16  17
3     18  19  20  21  22  23
4     24  25  26  27  28  29
5     30  31  32  33  34  35