Create an Index Based on an Underlying Categorical in Python Pandas

To create an Index based on an underlying Categorical, use the pandas.CategoricalIndex() method.

At first, import the required libraries −

import pandas as pd

CategoricalIndex is the Index based on an underlying Categorical. CategoricalIndex can only take on a limited, and usually fixed, number of possible values. Set the categories for the categorical using the "categories" parameter. Treat the categorical as ordered using the "ordered" parameter −

catIndex = pd.CategoricalIndex(
   ["p", "q", "r", "s","p", "q", "r", "s"], ordered=True, categories=["p", "q", "r", "s"]
)

Display the Categorical Index −

print("Categorical Index...\n",catIndex)

Get the categories −

print("\nDisplayingCategories from CategoricalIndex...\n",catIndex.categories)

Example

Following is the code −

import pandas as pd

# CategoricalIndex is the Index based on an underlying Categorical
# Set the categories for the categorical using the "categories" parameter
# Treat the categorical as ordered using the "ordered" parameter
catIndex = pd.CategoricalIndex(
   ["p", "q", "r", "s","p", "q", "r", "s"], ordered=True, categories=["p", "q", "r", "s"]
)

# Display the Categorical Index
print("Categorical Index...\n",catIndex)

# Get the categories
print("\nDisplayingCategories from CategoricalIndex...\n",catIndex.categories)

# Get the min value
print("\nMinimum value from CategoricalIndex...\n",catIndex.min())

# Get the max value
print("\nMaximum value from CategoricalIndex...\n",catIndex.max())

Output

This will produce the following output −

Categorical Index...
CategoricalIndex(['p', 'q', 'r', 's', 'p', 'q', 'r', 's'], categories=['p', 'q', 'r', 's'], ordered=True, dtype='category')

DisplayingCategories from CategoricalIndex...
Index(['p', 'q', 'r', 's'], dtype='object')

Minimum value from CategoricalIndex...
p

Maximum value from CategoricalIndex...
S