Python statistics Module
The Python statistics module is a built-in library that provides useful functions for performing common statistical calculations on numerical data. Instead of writing mathematical formulas manually, developers can use ready-made functions to calculate values such as mean, median, mode, and standard deviation.
Statistical calculations are commonly required when analyzing datasets, identifying patterns, understanding the center of data, and measuring how values are distributed. Python makes these tasks easier through the statistics module, which provides simple functions that can be used directly in Python programs.
In this article, we will explore some of the most commonly used functions of the Python statistics module, including mean(), median(), mode(), stdev(), median_low(), and median_high() with practical examples and outputs.
Table of Contents

What is the Python statistics Module?
The statistics module is part of Python’s standard library and is designed for calculating basic statistical properties of numerical datasets. Because it is included with Python, you can import it directly into your program without installing a separate package.
After importing the module, its functions can be accessed using the statistics name. For example:
import statistics
Once imported, functions such as statistics.mean(), statistics.median(), and statistics.stdev() can be used for statistical calculations.
1. Calculating the Mean with mean()
The mean() function calculates the arithmetic average of the values contained in a dataset. The mean is one of the most commonly used measures for describing the central tendency of numerical data.
To calculate the mean, add all the values together and divide their total by the number of values. The statistics.mean() function performs this calculation automatically.
Example
import statistics
# List of positive integers
datasets = [5, 2, 7, 4, 2, 6, 8]
x = statistics.mean(datasets)
print("Mean is:", x)
Output:
Mean is : 4.857142857142857
In this example, the mean() function calculates the average of all values in the datasets list. The resulting value gives a general indication of the center of the dataset.
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2. Finding the Median with median()
The median() function returns the middle value of a dataset. Before determining the middle position, the values are considered in sorted order.
When a dataset contains an odd number of values, there is one value directly in the middle. When the dataset contains an even number of values, there are two middle values, and their average is returned as the median.
Example
import statistics
datasets = [4, -5, 6, 6, 9, 4, 5, -2]
print("Median of dataset is:", statistics.median(datasets))
Output:
Median of dataset is: 4.5
Here, the dataset contains an even number of values. The two middle values after sorting are used to calculate the resulting median of 4.5.
The median can be useful for understanding the center of data, particularly when the values contain differences that can influence the arithmetic average.
3. Identifying the Mode with mode()
The mode() function is used to identify the value that occurs most frequently in a dataset. Unlike the mean and median, which describe the center of the data numerically, the mode focuses on the value that appears repeatedly.
This can be useful when you want to identify a common or frequently occurring value within a collection of data.
Example
import statistics
# Data set with repeated values
dataset = [2, 4, 7, 7, 2, 2, 3, 6, 6, 8]
print("Calculated Mode:", statistics.mode(dataset))
Output:
Calculated Mode: 2
In this example, the value 2 occurs more frequently than the other values in the dataset. Therefore, the mode() function returns 2.
4. Calculating Standard Deviation with stdev()
The stdev() function calculates the standard deviation of a sample dataset. Standard deviation is used to describe how spread out values are in relation to the mean.
A smaller standard deviation generally indicates that the values are closer to the mean, while a larger value indicates greater variation among the observations.
Example
import statistics
sample = [7, 8, 9, 10, 11]
print("Standard Deviation of sample is:", statistics.stdev(sample))
Output:
Standard Deviation of sample is: 1.5811388300841898
In this example, stdev() measures the amount of variation in the sample values. The returned result provides an indication of how far the values are distributed around their mean.
5. Finding the Low Median with median_low()
The median_low() function is another way to find a central value in a dataset. When the number of values is even, there are two middle values. Instead of calculating their average, median_low() returns the lower of those two middle values.
Example
import statistics
set1 = [4, 6, 2, 5, 7, 7]
print("Low median of dataset is:", statistics.median_low(set1))
Output:
Low median of dataset is: 5
After considering the values in sorted order, the two central values are identified. The lower one is returned by median_low().
This function can be useful when the lower central value is required instead of the average of the two middle values.
6. Finding the High Median with median_high()
The median_high() function works similarly to median_low(), but it returns the higher of the two middle values when a dataset contains an even number of elements.
Example
import statistics
dataset = [2, 1, 7, 6, 1, 9]
print("High median of dataset is:", statistics.median_high(dataset))
Output:
High median of dataset is: 6
In this example, the dataset contains six values. After arranging the values in order, the two central values are identified, and median_high() returns the higher one.
Difference Between Common statistics Functions
| Function | Purpose | Result |
|---|---|---|
mean() | Calculates the arithmetic average. | Average value |
median() | Finds the central value. | Middle value or average of two middle values |
mode() | Finds the most frequently occurring value. | Most common value |
stdev() | Measures variation in a sample. | Standard deviation |
median_low() | Returns the lower middle value. | Lower central value |
median_high() | Returns the higher middle value. | Higher central value |
Why Use the Python statistics Module?
The statistics module is useful because it provides ready-to-use functions for several common statistical operations. Developers do not need to manually write the formulas for basic calculations every time they need to analyze a dataset.
It can be useful when working with numerical collections and when a Python program needs to calculate central values or measure variation. Functions such as mean(), median(), and mode() can help summarize data, while stdev() can provide information about the spread of sample values.
Conclusion
The Python statistics module provides a convenient collection of functions for performing common statistical calculations. It can be imported directly into a Python program and used with numerical datasets.
In this guide, we explored important functions including mean() for calculating an arithmetic average, median() for finding the central value, mode() for identifying the most frequently occurring value, and stdev() for measuring sample variation. We also covered median_low() and median_high() for selecting lower and higher middle values from an even-sized dataset.
Understanding these functions provides a useful foundation for performing basic statistical analysis in Python and makes it easier to work with numerical data in programming projects.
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FAQs
1. What is the statistics module in Python?
The statistics module is a built-in Python library that provides functions for performing common statistical calculations on numerical data.
2. How do you import the statistics module in Python?
You can import the module using the following statement:
import statistics
3. What is the use of statistics.mean()?
The statistics.mean() function calculates the arithmetic average of the values in a dataset.
4. What does statistics.median() do?
The statistics.median() function returns the middle value of a dataset. If there are two middle values, it returns their average.
5. What is the purpose of statistics.mode()?
The statistics.mode() function identifies the most frequently occurring value in a dataset.
6. What does statistics.stdev() calculate?
The statistics.stdev() function calculates the standard deviation of a sample dataset and provides a measure of its variation.
7. What is the difference between median_low() and median_high()?
When a dataset contains an even number of values, median_low() returns the lower middle value, while median_high() returns the higher middle value.
8. Do you need to install the statistics module separately?
The statistics module is included in Python’s standard library, so it can normally be imported directly without installing a separate package.
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