In Which We Learn to Code

[writerkit]

Ever have those days where you are absolutely certain you have somehow messed up the process despite getting something that produces the answer the book asks for?

I am learning about lists and loops in my Python book. Logically this specific exercise is clearly an extension of the whole "x = x + 1" conceptual problem which I had to get Mathfriend to explain to me in very small words but have a good handle on now.

You are given a list: xs = [12, 10, 32, 3, 66, 17, 42, 99, 20]

The assignment is to find the product of the list using a loop.

This works:

total = int(1)
for xs in [12, 10, 32, 3, 66, 17, 42, 99, 20]:
    total = int(total * xs)

print(total)

It produces the desired result. If you omit setting total to 1 at the beginning it complains about total being undefined farther down, which I get. It depends on itself; it needs to start at something. And setting it to start at 1 doesn't mess with the end result. (The previous exercise was addition and it started at zero.)

I cannot shake the feeling I am getting some part of this wrong in some way, possibly in this being the wrong approach to it, but I can't figure out another possible one with the terms the book has described so far. Especially when the addition exercise did explicitly say "set it to zero to start." I just feel like a more elegant way to do it should exist.

(Also welcome to the posts where I complain about my coding lessons. Particularly in self-teaching I find it easier to actually sit down to do things if I'm writing up a Dreamwidth post about them, so you'll be getting some chronicling of my Adventures in Code coming up.)

Comments

[jducoeur]

The more elegant way to do it is with recursion, which requires the ability to create functions, something that I'm guessing your Python tutorial hasn't explained yet (when I learned programming at Wellesely, they taught recursion first, and loops as an extension of recursion, but this is not commonly the way that it's done).

Oh, good for them! That's the right computer-science way to do it, and modern functional-programming courses often start that way (I'm currently facilitating a Scala course for a diverse group at work that does that), but it's still uncommon, yes.

[elusiveat]

Yeah, I feel pretty good about having had that as my first training in CS.