# import necessary libraries
import pandas as pd

# create a sample df
df = pd.DataFrame({'A': [1, 2, 3],
                   'B': [4, 5, 6], 
                   'C': [7, 8, 9]})

# use columns.values and change 'A' & 'B'
# A is at index 0 (first col), and B is at 1
df.columns.values[0] = 'NewA'
df.columns.values[1] = 'NewB'

# print the result
print(df)