Cut in pandas

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

l = np.arange(1, 20)
l

array([ 1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17,
       18, 19])

pd.cut(l, bins=3)

[(0.982, 7.0], (0.982, 7.0], (0.982, 7.0], (0.982, 7.0], (0.982, 7.0], ..., (13.0, 19.0], (13.0, 19.0], (13.0, 19.0], (13.0, 19.0], (13.0, 19.0]]
Length: 19
Categories (3, interval[float64]): [(0.982, 7.0] < (7.0, 13.0] < (13.0, 19.0]]

pd.cut(l, bins=3, labels=["small", "medium", "large"])

['small', 'small', 'small', 'small', 'small', ..., 'large', 'large', 'large', 'large', 'large']
Length: 19
Categories (3, object): ['small' < 'medium' < 'large']

df = pd.DataFrame(pd.cut(l, bins=3, labels=["small", "medium", "large"]))
df

df.value_counts().plot(kind='barh')
plt.show()