Pandas query rfind()

There are often times when I first need to find where a specific piece of data lives and then use that information to take another action.  

Suppose you have a DataFrame that contains a column called 'Address', which contains the full address of each person. You want to extract the zip code from each address, which appears after the last comma. You can use the rfind() method to find the index of the last comma in each string, and then extract the zip code using slicing.

Here's an example code snippet that demonstrates how to use rfind() to extract the zip code from each address:

import pandas as pd

# create a sample DataFrame
df = pd.DataFrame({
    'Name': ['Alice', 'Bob', 'Charlie'],
    'Address': ['123 Main St, Anytown, USA 12345', '456 Oak Ave, Othertown, USA 67890', '789 Maple Dr, Another Town, USA 54321']
})

# extract the zip code from the 'Address' column using rfind()
df['Zip Code'] = df['Address'].str.slice(df['Address'].str.rfind(',') + 2)

# display the updated DataFrame
print(df)

In this example, we use the rfind() method to find the index of the last comma in each string in the 'Address' column. We then use this index to extract the zip code from each address using the slice() method. Note that we add 2 to the index returned by rfind() to account for the space after the comma. This ensures that we only extract the zip code, and not any additional text that may appear after it. The resulting DataFrame contains a new column called 'Zip Code', which contains the extracted zip code from each address. This is just one example of how the rfind() method can extract information from strings in a pandas DataFrame.