Wednesday, April 16, 2014

SOLUTION Exercise 10: List overlap comprehensions

Exercise

This week's exercise was an old exercise (see Exercise 5), requiring the solution in a different way.
Take two lists, say for example these two:
a = [1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
b = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
and write a program that returns a list that contains only the elements that are common between the lists (without duplicates). Make sure your program works on two lists of different sizes. Write this in one line of Python.

Extra:
  • Randomly generate two lists to test this

Sample solution

Great example of a solution including the extras!
Posted by at
Labels: ,

5 comments:

  1. UnknownApril 18, 2014 at 9:02 AM

    I think the solution may be slightly incorrect. The question said without duplicates, and [i for i in a if i in b] will undoubtedly produce duplicates. The reason there are no duplicates in the sample test is because random.sample takes UNIQUE numbers within that range.

    ReplyDelete
  2. UnknownApril 25, 2014 at 11:43 AM

    I had the same confusion!

    ReplyDelete
  3. UnknownApril 25, 2014 at 3:54 PM

    Hmm, good points on the solution. At the moment, I agree with Jamie that the /correct/ appropriate solution without using the random.sample arguments is to use:

    [i for i in set(a) if i in b]



    Even though technically I didn't talk about sets yet (nothing wrong with Googling!). It's not cheating to use something you find on Google, as long as you understand what it is you are doing.


    Thanks for pointing out the mistake. Any headway on finding a better solution without using sets? I'm stumped.

    ReplyDelete
  4. UnknownApril 25, 2014 at 4:29 PM

    Nope! I wracked my brains, searched google for ages. I also asked my brother (who is a Python Developer) and his response was "yeah, I'd just use sets..."

    ReplyDelete
  5. UnknownJuly 16, 2014 at 10:36 PM

    Yes, as ConfusedProgrammer said it would add duplicates to the result list if we don't randomise. I am yet to find a single line solution for the list overlap (exercise 5 ) using list comprehension. It would add duplicates if we don't randomise. Any suggestions?

    ReplyDelete

Subscribe to: Post Comments (Atom)