- looping over keys and indices with `enumerate()` - list, set and dictionary comprehension: filter and transform `[ x*x for x in range(0,10) if x % 2 == 0]` - vs. generator expression `(x*x for x in range(0,big_number) if x % 2 == 0)`
enumerate()[ x*x for x in range(0,10) if x % 2 == 0](x*x for x in range(0,big_number) if x % 2 == 0)