it is quite simple in pandas, but as a said in another comment, your example is a bit weird, since it turns all values of x into the same. But this is how to do

it is quite simple in pandas, but as a said in another comment, your example is a bit weird, since it turns all values of x into the same. But this is how to do it: df.assign(x = lambda x: x.ix[2, 'y']).query('x > 3')