Trusted answers to developer questions
Trusted Answers to Developer Questions

Related Tags

pandas
python
communitycreator

How to use nunique() function on a dataframe in pandas

Sheza Naveed

DataFrame

A DataFrame is a commonly used 2-dimensional data structure. It is a table that consists of columns and rows, and is used primarily as an object in the pandas library.

Sample dataframe

How to import the pandas library

We use the following statement to call the pandas library.


import pandas as pd

Example

A DataFrame can be formed as shown below. The one we use contains countries that have been put in different groups and are given a different a_score and b_score.

Both the scores are imaginary values for this example.

import pandas as pd

a_score = [4, 5, 7, 8, 2, 3, 1, 6, 9, 10]
b_score = [1, 2, 3, 4, 5, 6, 7, 10, 8, 9]

country = ['Pakistan', 'USA', 'Canada', 'Brazil', 'India', 'Beligium', 'Malaysia', 'Peru', 'England', 'Scotland']
groups = ['A','A','B','A','B','B','C','A','C','C']

df = pd.DataFrame({'group':groups, 'country':country, 'a_score':a_score, 'b_score':b_score})
print(df)
An example dataframe

The nunique() function

The nunique() function counts the number of unique entries in a column of a dataframe.

It is useful in situations where the number of categories is unknown beforehand.

Syntax

The function prototype is as follows.


mynumber = df.nunique()

Parameter

It does not take any parameters.

Return value

This method returns the number of entries in the requested columns.

Example

The following example prints the number of unique entries in a_score. Next, it prints a number of unique entries in all columns.

import pandas as pd

a_score = [4, 5, 7, 4, 2, 4, 1, 1, 5, 10]
b_score = [1, 2, 3, 4, 3, 6, 4, 10, 1, 9]

country = ['Pakistan', 'USA', 'Canada', 'Brazil', 'India', 'Beligium', 'Malaysia', 'Peru', 'England', 'Scotland']
groups = ['A','A','B','A','B','B','C','A','C','C']

df = pd.DataFrame({'group':groups, 'country':country, 'a_score':a_score, 'b_score':b_score})
print("the main dataframe")
print(df)

print("")
print("unique entries in a_score = ")
print(df.a_score.nunique())

print("")
print("unique entries in all columns = ")
print(df.nunique())
nunique function

RELATED TAGS

pandas
python
communitycreator
RELATED COURSES

View all Courses

Keep Exploring