Python Pandas - Get the levels in MultiIndex

To get the levels in MultiIndex, use the MultiIndex.levels property in Pandas. MultiIndex is a multi-level, or hierarchical, index object for pandas objects that allows you to work with higher dimensional data efficiently.

Syntax

MultiIndex.levels

This property returns a list of arrays, where each array contains the unique values for that index level.

Creating a MultiIndex

First, let's create a MultiIndex from arrays ?

import pandas as pd

# Create arrays for MultiIndex
arrays = [[1, 2, 3, 4, 5], ['John', 'Tim', 'Jacob', 'Chris', 'Keiron']]

# Create MultiIndex with named levels
multiIndex = pd.MultiIndex.from_arrays(arrays, names=('ranks', 'student'))

# Display the MultiIndex
print("The Multi-index...")
print(multiIndex)

The Multi-index...
MultiIndex([(1, 'John'),
            (2, 'Tim'),
            (3, 'Jacob'),
            (4, 'Chris'),
            (5, 'Keiron')],
           names=['ranks', 'student'])

Getting the Levels

Now, let's extract the levels from our MultiIndex ?

import pandas as pd

# Create arrays for MultiIndex
arrays = [[1, 2, 3, 4, 5], ['John', 'Tim', 'Jacob', 'Chris', 'Keiron']]

# Create MultiIndex with named levels
multiIndex = pd.MultiIndex.from_arrays(arrays, names=('ranks', 'student'))

# Get the levels in MultiIndex
print("The levels in Multi-index...")
print(multiIndex.levels)

The levels in Multi-index...
[[1, 2, 3, 4, 5], ['Chris', 'Jacob', 'John', 'Keiron', 'Tim']]

Understanding the Output

The levels property returns a list containing:

• First level: [1, 2, 3, 4, 5] - the unique values from the 'ranks' level
• Second level: ['Chris', 'Jacob', 'John', 'Keiron', 'Tim'] - the unique values from the 'student' level (sorted alphabetically)

Accessing Individual Levels

You can access specific levels using indexing ?

import pandas as pd

arrays = [[1, 2, 3, 4, 5], ['John', 'Tim', 'Jacob', 'Chris', 'Keiron']]
multiIndex = pd.MultiIndex.from_arrays(arrays, names=('ranks', 'student'))

# Access first level (ranks)
print("First level (ranks):", multiIndex.levels[0])

# Access second level (student)
print("Second level (student):", multiIndex.levels[1])

First level (ranks): [1, 2, 3, 4, 5]
Second level (student): ['Chris', 'Jacob', 'John', 'Keiron', 'Tim']

Conclusion

The MultiIndex.levels property provides access to the unique values at each level of a hierarchical index. Each level contains sorted unique values, making it useful for understanding the structure of your MultiIndex data.