Pandas: create new column in df with random integers from range

One solution is to use numpy.random.randint:

import numpy as np
df1['randNumCol'] = np.random.randint(1, 6, df1.shape[0])

Or if the numbers are non-consecutive (albeit slower), you can use this:

df1['randNumCol'] = np.random.choice([1, 9, 20], df1.shape[0])

In order to make the results reproducible you can set the seed with numpy.random.seed (e.g. np.random.seed(42))