List comprehensions: map och filter med syntax

Ett smidigt sätt att utföra map och/eller filter:
    [x*10 for x in [1,2,3,4]] # -> [10,20,30,40]
    [x for x in [1,2,3,4] if x % 2] # -> [1,3]
    
    [x*10 for x in [1,2,3,4] if x % 2] # -> [10,30]
    
    [(x,y) for x in [1,2,3] for y in ["a","b"]]
    # -> [(1, 'a'), (1, 'b'),
    #     (2, 'a'), (2, 'b'),
    #     (3, 'a'), (3, 'b')]