Cut a variable with pandas.

cut.py

import pandas as pd
from sklearn import datasets
iris = datasets.load_iris()

iris_df = pd.DataFrame(iris.data, columns=iris.feature_names)
iris_df['species'] = iris.target
mapping = {0 : 'setosa', 1: 'versicolor', 2: 'virginica'}
iris_df = iris_df.replace({'species': mapping})

iris_df['sepal length (bins)'] = pd.cut(iris_df['sepal length (cm)'], bins=[0, 3, 6, 9], include_lowest=False, right=True)