How to retrieve the last valid index from a series object using pandas series.last_valid_index() method?

The pandas series.last_valid_index() method is used to get the index of the last valid element from the given series object. This means the last_valid_index() method returns the index of the last non_null element of the series.

It will return a single scalar based on the type of series index, and it will return None if the given series has all null/NA values or if it is empty. The method doesn’t have any parameters.

Example 1

Let’s create a pandas series object and retrieve the last valid index by using the last_valid_index() method.

# importing packages import pandas as pd import numpy as np # create a series s = pd.Series([None, 34, np.nan, 87], index=list('pqrs')) print(s) # apply last_valid_index() method result = s.last_valid_index() print("Result:") print(result)

Output

The output is as follows −

p    NaN q    34.0 r    NaN s    87.0 dtype: float64 Result: s

For the above example, the last valid index is “s”, because the element at index position s is not a Null/NA value.

Example 2

Here, let’s take an empty series object and see how the last_valid_index() method works for an empty series.

# importing packages import pandas as pd # create an empty series sr = pd.Series([]) print(sr) # apply last_valid_index() method result = sr.last_valid_index() print("Result:") print(result)

Output

The output is mentioned below −

Series([], dtype: float64) Result: None

The last_valid_index() method returned None for the empty series object.

Example 3

In this following example, we have created a pandas series object with all Null/Nan values and applied the last_valid_index() method to get the last valid index.

# importing packages import pandas as pd import numpy as np # create a series sr = pd.Series([None, np.nan]) print(sr) # apply last_valid_index() method result = sr.last_valid_index() print("Result:") print(result)

Output

The output is given below −

0    NaN 1    NaN dtype: float64 Result: None

For this example, the last_valid_index() method returned None, because there is no valid element available in the given series object.