traversing nested lists, need help in python

Question

If I have a list now can I get all of the items out of the lists? The catch is for me, that it has lists within the lists and both integers and strings in the list. Thanks

python
test = [1, 2, [0, [3, 5, 'weather'], 1], 'hats', [0, 1]]

How can you pull out so it prints like this... (1, 2, 0, 3, 5, 'weather', 1, 'hats', 0, 1)

Answer 1 · 2017-03-12T21:42:31Z

March 12, 2017 9:42pm

This seems like a good use for recursion. If you've never come across recursion before, it's a really interesting subject to read up on. The important thing to know for the purposes of this problem is that we will write a function that calls itself every time it comes across a nested list inside the list it's traversing. By appending non-list items when you come across them, and extending the outer list with the inner list when you come across a list, you'll end up with the result you're after. You can try it with an even deeper nested list than the one you've given in the example and this code will still work. It's not very easy to explain in a few lines, you might be better off just reading up on the subject if it's completely new to you:

http://openbookproject.net/thinkcs/python/english3e/recursion.html

Here's my solution - line 5 is where the magic happens, as the function calls itself to get to work on the inner list.

def combine(input_list):
  output_list = []
  for item in input_list:
    if type(item) is list:
      output_list.extend(combine(item))
    else:
      output_list.append(item)
  return output_list

combined_list = combine(test_list)

print(combined_list)

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Adam Harms

Adam Harms

traversing nested lists, need help in python

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Stuart Wright

Stuart Wright