immutability

I have this API function: public ResultEnum DoSomeAction(string a, string b, DateTime c, OtherEnum d, string e, string f, out Guid code) I don't like it. Because parameter order becomes unnecessarily significant. It becomes harder to add new fields. It's harder to see what's being passed around. It's harder to refactor method into smaller parts because it creates another overhead of passing all the parameters in sub functions. Code is harder to read. I came up with the most obvious idea: have an object encapsulating the data and pass it around instead of passing each parameter one by one. Here

Can someone explain why the example with integers results in different values for x and y and the example with the list results in x and y being the same object? x = 42 y = x x = x + 1 print x # 43 print y # 42 x = [ 1, 2, 3 ] y = x x[0] = 4 print x # [4, 2, 3] print y # [4, 2, 3] x is y # True Because integers are immutable, while list are mutable. You can see from the syntax. In x = x + 1 you are actually assigning a new value to x (it is alone on the LHS). In x[0] = 4 , you're calling the index operator on the list and giving it a parameter - it's actually equivalent to x.__setitem__(0, 4)