Python Pandas - Count the number of rows in each group

Use the group.size() to count the number of rows in each group. Import the required library −

import pandas as pd

Create a DataFrame −

dataFrame = pd.DataFrame({'Product Category': ['Computer', 'Mobile Phone', 'Electronics', 'Electronics', 'Computer', 'Mobile Phone'],'Quantity': [10, 50, 10, 20, 25, 50],'Product Name': ['Keyboard', 'Charger', 'SmartTV', 'Camera', 'Graphic Card', 'Earphone'] })

Group by columns −

dataFrame.groupby(["Product Category", "Quantity"]) 

Now, count the group size to get the count of rows in each group.

Example

Following is the complete code −

import pandas as pd # create a dataframe dataFrame = pd.DataFrame({'Product Category': ['Computer', 'Mobile Phone', 'Electronics', 'Electronics', 'Computer', 'Mobile Phone'],'Quantity': [10, 50, 10, 20, 25, 50],'Product Name': ['Keyboard', 'Charger', 'SmartTV', 'Camera', 'Graphic Card', 'Earphone'] }) # dataframe print"Dataframe...\n",dataFrame # grouping columns new_group = dataFrame.groupby(["Product Category", "Quantity"]) # group size new_group = new_group.size() # dataframe print"\nUpdated Dataframe...\n",new_group

Output

This will produce the following output −

Dataframe...    Product Category   Product Name   Quantity 0          Computer       Keyboard         10 1      Mobile Phone        Charger         50 2       Electronics        SmartTV         10 3       Electronics         Camera         20 4          Computer   Graphic Card         25 5      Mobile Phone       Earphone         50 Updated Dataframe... Product Category   Quantity Computer           10        1                    25        1 Electronics        10       1                    20 1 Mobile Phone       50 2 dtype: int64