python-3.x - PythonBasics: How to select a substring from a series in a dataframe

Question

I am not sure how to select a substring from a series in a dataframe to extract some needed text.

Example: I have a 2 series in the dataframe and am trying to extract the last portion of the string in QRY series that will have "AND" string.

So If I have "This is XYZ AND y = 1" then I need to extract "AND y = 1".

For this I've chosen rfind("AND") since the AND can occur anywhere in string but I need the highest index and then wants to extract the string that begins with the highest index AND.

Sample for one string

   strg = "This is XYZ AND y = 1"
    print(strg[strg.rfind("AND"):]) 
-- This is working, but on a data frame its saying cannot do slice indexing on <class 'pandas.core.indexes.range.RangeIndex'

data set

import pandas as pd 
data = {"CELL":["CELL1","CELL2","CELL3"], "QRY": ["This is XYZ AND y = 1","No that is not AND z = 0","Yay AND a= -1"]}
df = pd.DataFrame(data,columns = ["CELL","QRY"])
print(df.QRY.str.rfind("AND"))