How To Count unique values in a column in pandas dataframe?

While we have multiple Columns in our Dataframe, What if we need to count Unique values from a particular column? So in this tutorial, we are going to learn about How To Count unique values in a column in pandas dataframe? Let’s get started with this tutorial without wasting your time.

How To Count unique values in a column in pandas dataframe?

Method 1: Use nunique

Here, for example, I have the following data frame with marks.

df = pd.DataFrame({
  'science': [97, 96, 95, 97, 96, 94, 96, 97],
  'maths': [80, 81, 82, 79, 81, 83, 80, 79],
})

And if I want to count unique values in a column in pandas dataframe then nunique we can Use. Just Use your Column name and put .unique() just like this.

df['science'].nunique()
4

And This is How we can Count the Unique value of the dataframe column. Thanks.

Method 2: Use pd.DataFrame.agg

You can Also Use pd.DataFrame.agg just like this. We are using the same example as I mentioned in method 1.

df.agg(['count', 'size', 'nunique'])

         science  maths
count         8      8
size          8      8
nunique       4      5

Just put [‘count’, ‘size’, ‘nunique’] into pd.DataFrame.agg and it will return you total_count of the column, total_size of columns, and total_unique value count. Hope You understand. Thanks.

Method 3: Use this

Also You can Count unique values in a column in pandas dataframe using unique(). Just like this.

len(df.science.unique())

And it will return the Count of Unique value.

Conclusion

It’s all About this article. Hope this method worked for you. Comment below Your thoughts and your queries. Also, Comment below which method worked for you?

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