How to perform a group by function in Python?

The groupby() function in Pandas is used to group rows based on a specific column and perform aggregate operations on them. Eternalwigs 

Steps to Perform groupby() in Pandas:

Create a DataFrame

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import pandas as pd

data = {'Company': ['GOOG', 'GOOG', 'MSFT', 'MSFT', 'FB', 'FB'],

        'Person': ['Sam', 'Charlie', 'Amy', 'Vanessa', 'Carl', 'Sarah'],

        'Sales': [200, 120, 340, 124, 243, 350]}

df = pd.DataFrame(data)

print(df)

This creates a DataFrame with three columns: Company, Person, and Sales.

Grouping by a Column

To group the data by Company, use:

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df.groupby('Company')

This returns a DataFrameGroupBy object, which can be used for further operations.

Applying Aggregate Functions

We can apply aggregation methods like mean(), sum(), count(), etc.

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by_comp = df.groupby("Company")

print(by_comp.mean()) # Calculates the average sales per company

This will return the mean Sales for each company.