How to Count Unique Values in Pandas (With Examples)

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How to Count Unique Values in Pandas (With Examples)

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You can use the nunique() function to count the number of unique values in a pandas DataFrame.

This function uses the following basic syntax:

#count unique values in each column df.nunique() #count unique values in each row df.nunique(axis=1)

The following examples show how to use this function in practice with the following pandas DataFrame:

import pandas as pd #create DataFrame df = pd.DataFrame({'team': ['A', 'A', 'A', 'A', 'B', 'B', 'B', 'B'], 'points': [8, 8, 13, 13, 22, 22, 25, 29], 'assists': [5, 8, 7, 9, 12, 9, 9, 4], 'rebounds': [11, 8, 11, 6, 6, 5, 9, 12]}) #view DataFrame df team points assists rebounds 0 A 8 5 11 1 A 8 8 8 2 A 13 7 11 3 A 13 9 6 4 B 22 12 6 5 B 22 9 5 6 B 25 9 9 7 B 29 4 12 Example 1: Count Unique Values in Each Column

The following code shows how to count the number of unique values in each column of a DataFrame:

#count unique values in each column df.nunique() team 2 points 5 assists 5 rebounds 6 dtype: int64

From the output we can see:

The ‘team’ column has 2 unique values The ‘points’ column has 5 unique values The ‘assists’ column has 5 unique values The ‘rebounds’ column has 6 unique values Example 2: Count Unique Values in Each Row

The following code shows how to count the number of unique values in each row of a DataFrame:

#count unique values in each row df.nunique(axis=1) 0 4 1 2 2 4 3 4 4 4 5 4 6 3 7 4 dtype: int64

From the output we can see:

The first row has 4 unique values The second row has 2 unique values The third row has 4 unique values

And so on.

Example 3: Count Unique Values by Group

The following code shows how to count the number of unique values by group in a DataFrame:

#count unique 'points' values, grouped by team df.groupby('team')['points'].nunique() team A 2 B 3 Name: points, dtype: int64

From the output we can see:

Team ‘A’ has 2 unique ‘points’ values Team ‘B’ has 3 unique ‘points’ values Additional Resources

The following tutorials explain how to perform other common operations in pandas:

How to Count Observations by Group in Pandas How to Count Missing Values in Pandas How to Use Pandas value_counts() Function

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How to Count Unique Values in Pandas (With Examples)

How to Count Unique Values in Pandas (With Examples)

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