*34*

You can use the following methods to calculate the standard deviation by group in pandas:

**Method 1: Calculate Standard Deviation of One Column Grouped by One Column**

df.groupby(['group_col'])['value_col'].std()

**Method 2: Calculate Standard Deviation of Multiple Columns Grouped by One Column**

df.groupby(['group_col'])['value_col1', 'value_col2'].std()

**Method 3: Calculate Standard Deviation of One Column Grouped by Multiple Columns**

df.groupby(['group_col1', 'group_col2'])['value_col'].std()

The following examples show how to use each method 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'], 'position': ['G', 'F', 'F', 'G', 'F', 'F', 'G', 'G'], 'points': [30, 22, 19, 14, 14, 11, 20, 28], 'assists': [4, 3, 7, 7, 12, 15, 8, 4]}) #view DataFrame print(df) team position points assists 0 A G 30 4 1 A F 22 3 2 A F 19 7 3 A G 14 7 4 B F 14 12 5 B F 11 15 6 B G 20 8 7 B G 28 4

**Example 1: Calculate Standard Deviation of One Column Grouped by One Column**

The following code shows how to calculate the standard deviation of the **points** column, grouped by the **team** column:

#calculate standard deviation of points grouped by team df.groupby('team')['points'].std() team A 6.70199 B 7.50000 Name: points, dtype: float64

From the output we can see:

- The standard deviation of points for team A is
**6.70199**. - The standard deviation of points for team B is
**7.5**.

**Example 2: Calculate ****Standard Deviation ****of Multiple Columns Grouped by One Column**

The following code shows how to calculate the standard deviation of the **points** column and the standard deviation of the **assists** column, grouped by the **team** column:

#calculate standard deviation of points and assists grouped by team df.groupby('team')[['points', 'assists']].std() points assists team A 6.70199 2.061553 B 7.50000 4.787136

The output displays the standard deviation of the **points** column and the **assists** column for each team.

**Example 3: Calculate Standard Deviation of One Column Grouped by Multiple Columns**

The following code shows how to calculate the standard deviation of the **points** column, grouped by the **team** and **position** columns:

#calculate standard deviation of points, grouped by team and position df.groupby(['team', 'position'])['points'].std() team position A F 2.121320 G 11.313708 B F 2.121320 G 5.656854 Name: points, dtype: float64

From the output we can see:

- The standard deviation of points for players on team A and position F is
**2.12**. - The standard deviation of points for players on team A and position G is
**11.31**. - The standard deviation of points for players on team B and position F is
**2.12**. - The standard deviation of points for players on team B and position G is
**5.65**.

**Additional Resources**

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

How to Calculate Mean by Group in Pandas

How to Calculate Max Value by Group in Pandas

How to Calculate Sum by Group in Pandas

How to Calculate Quantiles by Group in Pandas