You can use the following basic syntax to perform a groupby and count with condition in a pandas DataFrame:

df.groupby('var1')['var2'].apply(lambda x: (x=='val').sum()).reset_index(name='count')

This particular syntax groups the rows of the DataFrame based on **var1** and then counts the number of rows where **var2** is equal to ‘val.’

The following example shows how to use this syntax in practice.

**Example: Groupby and Count with Condition in Pandas**

Suppose we have the following pandas DataFrame that contains information about various basketball players:

import pandas as pd #create DataFrame df = pd.DataFrame({'team': ['A', 'A', 'A', 'A', 'B', 'B', 'B', 'B'], 'pos': ['Gu', 'Fo', 'Fo', 'Fo', 'Gu', 'Gu', 'Fo', 'Fo'], 'points': [18, 22, 19, 14, 14, 11, 20, 28]}) #view DataFrame print(df) team pos points 0 A Gu 18 1 A Fo 22 2 A Fo 19 3 A Fo 14 4 B Gu 14 5 B Gu 11 6 B Fo 20 7 B Fo 28

The following code shows how to group the DataFrame by the **team** variable and count the number of rows where the **pos** variable is equal to ‘Gu’:

#groupby team and count number of 'pos' equal to 'Gu' df_count = df.groupby('team')['pos'].apply(lambda x: (x=='Gu').sum()).reset_index(name='count') #view results print(df_count) team count 0 A 1 1 B 2

From the output we can see:

- Team A has
**1**row where the pos column is equal to ‘Gu’ - Team B has
**2**rows where the pos column is equal to ‘Gu’

We can use similar syntax to perform a groupby and count with some numerical condition.

For example, the following code shows how to group by the **team** variable and count the number of rows where the **points **variable is greater than 15:

#groupby team and count number of 'points' greater than 15 df_count = df.groupby('team')['points'].apply(lambda x: (x>15).sum()).reset_index(name='count') #view results print(df_count) team count 0 A 3 1 B 2

From the output we can see:

- Team A has
**3**rows where the points column is greater than 15 - Team B has
**2**rows where the points column is greater than 15

You can use similar syntax to perform a groupby and count with any specific condition you’d like.

**Additional Resources**

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

How to Count Unique Values Using Pandas GroupBy

How to Apply Function to Pandas Groupby

How to Create Bar Plot from Pandas GroupBy