Using pandas.Series.mean() to compute the arithmetic mean of a Series

Updated: February 18, 2024 By: Guest Contributor Post a comment

Introduction to Pandas

Pandas is an open-source library providing high-performance, easy-to-use data structures, and data analysis tools for the Python programming language. Among its data structures, the Series object is designed to accommodate a sequence of one-dimensional data and comes coupled with an index. The mean() method, utilized on a Series object, calculates the arithmetic mean, ignoring NaN (Not a Number) values by default.

Are you looking to understand how to calculate the arithmetic mean of a data series using Pandas in Python? You’re in the right place. The Pandas library in Python is a powerhouse for data manipulation and analysis. In this tutorial, we will delve into the use of the Series.mean() method, exploring its functionality with a variety of examples ranging from basic to advanced usage scenarios.

Basic Usage of Series.mean()

Let’s start with a simple example. First, ensure you have Pandas installed:

pip install pandas

Now, let’s create a basic series:

import pandas as pd

# Creating a simple series
simple_series = pd.Series([1, 2, 3, 4, 5])

# Calculating the mean

This will output:


As evidenced, the method accurately calculates the mean of our data series. Next, let’s explore how the method deals with missing values.

Handling Missing Values

Missing values can often pose a challenge in data analysis. Thankfully, Series.mean() skillfully omits these values by default when calculating the mean:

import pandas as pd

# Creating a series with missing values
na_series = pd.Series([1, 2, 3, None, 5])

# Calculating the mean

This results in:


The method disregards the None value, providing an accurate mean of the remaining numbers.

Advanced Usage: Weighted Mean

Sometimes, merely calculating a simple mean doesn’t suffice; we might need to calculate a weighted mean. Here’s how you can achieve this using pandas.Series.mul() alongside mean():

import pandas as pd

# Creating two series, one for values and another for weights
values = pd.Series([1, 2, 3, 4])
weights = pd.Series([10, 1, 1, 1])

# Calculating weighted mean
weighted_mean = (values.mul(weights)).sum() / weights.sum()

The output will be:


This method meticulously calculates the weighted mean, signifying that not all values contribute equally to the final mean calculation.

Series.mean() with DateTime Data

Calculating the mean of DateTime series can also be insightful, especially for time series analysis. When applied to a DateTime series, Series.mean() computes the average timestamp:

import pandas as pd
import numpy as np

# Creating a DateTime series
date_series = pd.Series(pd.date_range('20210101', periods=4, freq='D'))

# Calculating the mean date (average timestamp)
mean_date = date_series.mean()

This results in a Timestamp:

2021-01-03 00:00:00

This capability showcases the method’s versatility, adapting its calculation based on the data type of the series.


The Series.mean() function in Pandas is an efficient tool for calculating the arithmetic mean across diverse scenarios, be it with simple numeric data, adjusting for missing values, applying weights, or even working with date/time information. This flexibility and efficiency make it an invaluable tool for data scientists and analysts working with Python.