Python Pandas - Compute indexer and mask for new index given the current index

To compute indexer and mask for new index given the current index, use the index.get_indexer() method in Pandas.

At first, import the required libraries −

import pandas as pd

Creating Pandas index −

index = pd.Index([10, 20, 30, 40, 50, 60, 70])

Display the Pandas index −

print("Pandas Index...\n",index)

Compute indexer and mask. Marked by -1, as it is not in index −

print("\nGet the indexes...\n",index.get_indexer([30, 40, 90, 100, 50]))

Example

Following is the code −

import pandas as pd

# Creating Pandas index
index = pd.Index([10, 20, 30, 40, 50, 60, 70])

# Display the Pandas index
print("Pandas Index...\n",index)

# Return the number of elements in the Index
print("\nNumber of elements in the index...\n",index.size)

# Compute indexer and mask
# Marked by -1, as it is not in index
print("\nGet the indexes...\n",index.get_indexer([30, 40, 90, 100, 50]))

Output

This will produce the following output −

Pandas Index...
Int64Index([10, 20, 30, 40, 50, 60, 70], dtype='int64')

Number of elements in the index...
7

Get the indexes...
[ 2 3 -1 -1 4]