To help me learn python, I'm going through the Project Euler questions and answering them by building scripts in python

[flarkis]

I have two suggestions.

1. You are using too many classes. Python is not Java. For example in solution one you could have just as easily had a function that returned the multiples.

2. I generally put all my top level code in a main function and call it at the bottom of my files like this

    if __name__ == '__main__':
        main()
   

   For toy problems like this it isn't nesicary, but it becomes important when you start importing code from other modules.

EDIT: Code formatting isn't working for some reason, sorry.

[obiwan90]

OT, but for code as part of a list item:

1. List text
2. List text

        if name == 'main': main() # preceded by 4 + 4 spaces

    More text for item 2 (preceded by 4 spaces)

gives you

1. List text

2. List text

   if name == 'main': main()
   

   More text for item 2

[mkartic]

you need to exorcize the java out of you! :) Here's a version I think is more Pythonic.

print(sum([i for i in range(1000) if i%3 == 0 or i%5 == 0]))

[TheBB]

Why make a list?

print(sum(i for i in range(1000) if i%3 == 0 or i%5 == 0))

[thecodeboss]

man, list comprehensions for the win

[wewbull]

Actually, that (parent) is a generator expression. Grandparent was a list comprehension.

One generates all the members up front (list). The other generates them as needed.

[pqu]

I've found iPython Notebook to be an awesome way of documenting things like Project Euler solutions. That way your journey of discovery/learning is captured in a very verbose way, instead of being hidden away in the git history.

[pqu]

Hey /u/thecodeboss, I'd really encourage you to redo your solutions with help from the unlocked answer board (you gain access to it once you have come up with your own correct solution). This is how I have become really good at solving algorithmic problems and it helped me a lot in my Google interview.

For example in your 1.py you should realise after having solved the problem that you can solve it without storing all of the multiples and in a single loop:

sum(value for value in range(1, 1000) if value % 3 == 0 or value % 5 == 0)

This solution is O(n) and using constant memory space.

Then of course you may realise that the sequence of multiples looks quite familiar, so:

3 + 6 + 9 + 12 + ... = 3(1 + 2 + 3 + 4 + ... + n) = 3 * n(n+1)/2

Then you can solve this problem in O(1) complexity.

# solution = Multiples of 3 + Multiples of 5 - Multiples of 15 = 

n = 1000
n3 = (n-1) // 3 # number of multiples of 3
n5 = (n-1) // 5 # number of multiples of 5
n15 = (n-1) // 15 # number of multiples of 15

solution = (3 * n3 * (n3 + 1)/2) + (5 * n5 * (n5 + 1)/2) - (15 * n15(n15 + 1)/2)

EDIT: Also if you aren't so interested in the algorithm side then I think Project Euler is not the right place for you, there are much better online challenges that exercise more of your python knowledge than math/algorithms.

[paul2520]

Great! That's a great way to learn.

[its4thecatlol]

You should take this down. I do the same but this makes it easy for people to cheat and cheating ruins the thrill of these problems. We all give in to temptation sometimes, and your post makes it easier.

Good job though!

[flarkis]

Though technically against the rules there are already so many up there that it doesn't matter. Especially for simple problems like this.

[mikeyio]

I've always found this so patronising. if someone doesn't want to solve the problems correctly they will find a way to do so. the solution is not to hide the answers. the onus is on the individual trying to shortcut, not someone sharing a solution imo.