nunique pandas – Get Number of Unique Values in DataFrame

To get the number of unique values in a pandas DataFrame or Series, the simplest way is to use the pandas nunique() function.

df["variable"].nunique()

When working with data as a data science or data analyst, it’s important to be able to find the basic descriptive statistics of a set of data.

One basic descriptive statistic which is important is the number of unique values in a dataset.

To get the number of unique values in a DataFrame, we can use the pandas nunique() function.

The following code will get you the count of unique values of a series in Python:

df["variable"].nunique()

If you want to get the number of unique values of an entire DataFrame in pandas, you can call nunique() in the following way:

df.nunique()

Getting the Count of Unique Values of All Columns in DataFrame Using Pandas

Let’s say I have the following pandas DataFrame:

     Name  Weight_Change Month
0     Jim         -16.20     1
1   Sally          12.81     1
2     Bob         -20.45     1
3     Sue          15.35     1
4    Jill         -12.43     1
5   Larry         -18.52     1
6     Jim          -6.10     2   
7   Sally          -2.81     2  
8     Bob          12.45     2
9     Sue          -0.32     2
10   Jill          -1.23     2
11  Larry          -8.52     2
12    Jim           5.20     3 
13  Sally          12.81     3  
14    Bob          -2.45     3
15    Sue           5.35     3
16   Jill          -2.43     3
17  Larry          -1.85     3

We can call the nunique function on the DataFrame to get the number of unique values for all of the columns.

print(df.nunique())

Name              6
Weight_Change    18
Month             3
dtype: int64

Getting the Count of Unique Values of a Column Using Pandas

Let’s say we only want to get the count of unique values of a single column in a pandas DataFrame.

In the DataFrame above, let’s get the count of unique values for the column “Month”, and the column “Name”. We should expect 3 and 6, respectively.

To get the count of unique values, I can do the following in my python code:

print(df["Month"].nunique())
print(df["Name"].nunique())

#Output:
3
6

Hopefully this article has been useful for you to find the number of unique values in a pandas DataFrame using Python.