How to use variable in a query in pandas

Suppose you want to reference a variable in a query in pandas package in Python. This seems to be a straightforward task but it becomes daunting sometimes. Let's discuss it with examples in the article below.

Let's create a sample dataframe having 3 columns and 4 rows. This dataframe is used for demonstration purpose.

import pandas as pd
df = pd.DataFrame({"col1" : range(1,5), 
                   "col2" : ['A A','B B','A A','B B'],
                   "col3" : ['A A','A A','B B','B B']
                   })

Filter a value A A in column col2

In order to do reference of a variable in query, you need to use @.

Mention

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