mode() function in Python statistics module

The mode of a set of data values is the value that appears most frequently. In statistics, it’s often used to understand the most common or popular value within a set. A mode of a continuous probability distribution is often considered to be any value 'x' at which its probability density function has a local maximum value, so any peak is a mode.

A dataset can have:

• One mode (unimodal),
• More than one mode (multimodal),
• Or no mode (if all values are unique).

Python’s built-in statistics module provides a convenient mode() function to compute this directly, for example:

import statistics

a = [1, 2, 3, 4, 4, 4, 5, 6, 7, 7, 7]
res = statistics.mode(a)
print("Mode:", res)

Mode: 4

Explanation: mode() method returns 4 from the list because it is the first value with the highest frequency.

Syntax

statistics.mode(data)

Parameters:

• data: A list, tuple, or any iterable containing numeric or string values.

Return Type: It returns the most frequent value from the dataset.

Raises: StatisticsError if the dataset is empty.

In Python versions prior to 3.8, statistics.mode() raises a StatisticsError if there is more than one most common value (no unique mode). From Python 3.8 onwards, statistics.mode() returns the first mode encountered in case of multiple values with equal highest frequency. For reliable multi-mode analysis, use statistics.multimode().

Examples of mode()

Example 1: Mode with Different Datatypes

In this example, we will use mode() method over iterables containing various range of datatypes:

from statistics import mode
from fractions import Fraction as fr

d1 = (2, 3, 3, 5, 5, 5, 6)
d2 = (2.4, 1.3, 1.3, 2.4, 1.3)
d3 = (fr(1, 2), fr(1, 2), fr(2, 3))
d4 = (-2, -2, -7, -7, -2)
d5 = ("red", "blue", "blue", "black", "black", "black")

print("Mode 1:", mode(d1))
print("Mode 2:", mode(d2)) 
print("Mode 3:", mode(d3))  
print("Mode 4:", mode(d4))  
print("Mode 5:", mode(d5)) 

Mode 1: 5
Mode 2: 1.3
Mode 3: 1/2
Mode 4: -2
Mode 5: black

Explanation:

• For every iterable, mode() method returns the element with the greatest frequency.
• If there the elements with equal freqency greater than the others then it return the first occurring one in the iterable.

Example 2: Mode on an Empty List

Mode method throws a StatisticsError if appliead over an empty iterable.

import statistics

a = [] 

print(statistics.mode(a))

Output

Hangup (SIGHUP)
Traceback (most recent call last):
  File "/home/guest/sandbox/Solution.py", line 5, in <module>
    print(statistics.mode(a))
          ~~~~~~~~~~~~~~~^^^
  File "/usr/local/lib/python3.13/statistics.py", line 785, in mode
    raise StatisticsError('no mode for empty data') from None
statistics.StatisticsError: no mode for empty data

Example 3: Mode in a Real-World Context

In this example, mode() is used to determine the most popular subject among students:

from statistics import mode

s = ["Math", "Science", "English", "Math", "History", "Math", "Science"]

print("Most liked subject is:", mode(s))

Most liked subject is: Math

Explanation:

• "Math" appears 3 times, which is more than any other subject.
• So, the mode is "Math".

Also read: probability density function, local maximum value,statistics module

retr0

Follow

Improve

Article Tags :

• Python
• DSA
• Python-Built-in-functions

Practice Tags :

• python