Examples
import numpy as np
import pandas as pd
df = pd.DataFrame([[2, 3, 4], [0, 5, 6], [20, 30, 40]],
columns=['P', 'Q', 'R'])
df
Get value at specified row/column pair
df.iat[2, 2]
Set value at specified row/column pair
df.iat[2, 2] = 10
df.iat[2, 2]
Get value within a series
df.loc[0].iat[2]