# Combination Function Help

Mark Lawrence breamoreboy at yahoo.co.uk
Wed Feb 12 16:40:48 CET 2014

```On 12/02/2014 15:20, kjakupak at gmail.com wrote:
> So I need to write a function based off of nCr, which I have here:
>
> def choices(n, k):
>      if n == k:
>          return 1
>      if k == 1:
>          return n
>      if k == 0:
>          return 1
>      return choices(n - 1, k) + choices(n - 1, k - 1)
>
> It works fine, but then I need to add in so that the user can have an input box for n and k.
>
> def choices(n, k):
>      if k == 1:
>          return n
>      if n == k:
>          return 1
>      if k == 0:
>          return 1
>      return choices(n - 1, k) + choices(n - 1, k - 1)
>
> n_input = int(input("Number of courses you like: "))
> k_input = int(input("Number of courses you can register for: "))
>
> The above doesn't return any value at all. And then I need it to print the total number of ways of choosing k out of n courses, which I only have:
>
> print ("Total number of ways of choosing %d out of %d courses: " % (n_input, k_input))
>
>
> So basically I need help figuring out why it won't return any value and how to print that final value.
>

Actually calling choices with n_input and k_input as inputs might help

--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence

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```