Allan is debugging a script and notices a for loop used to validate some element. Which element could use this snippet of code for validation?​

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?

How many types of string types does python support?

Consider a list of full names formatted “firstname lastname”, like ["jules verne", "alexandre dumas", "maurice druon"]. write a list comprehension that produces a list with the full names in the format “lastname, firstname”. the resulting list should look like ['verne, jules', 'dumas, alexandre', 'druon, maurice']. the simplest solution may involve a nested comprehension: [ …. for … in [ … for … in … ]].