Question

I asked a while ago about how to make a list of sublists (and of even more sublists) from a string given delimiters here.
How to process a string into layer of sublists

Now, I need to join them back together and I’m not sure how. I have tried to look here
Python : Recursively flatten a list
and
Flatten a list in python

However, neither of these answers work in my case because chain splits my string (single item “lists”) into characters, and then therefore cannot join with “\n”, and reduce does not concatenate str and list objects.

I will probably need to walk through the sublists (and their sublists) at some point. Is there a way to iterate through each level of sublist? (I can leave this as a separate question, one step at a time.. but just wondering whether this process is making sense or should I try an entire new method. I do think logically this makes the most sense, I’m just having trouble navigating it.)

Thanks.

Answer 1

I’m going to assume what I said in the comment is correct unless you say otherwise.

From the posts you linked, you have:

import collections

def flatten(l):
    for el in l:
        if isinstance(el, collections.Iterable) and not isinstance(el, basestring):
            for sub in flatten(el):
                yield sub
        else:
            yield el

to recursively flatten an irregular list of lists, and

def go(it):
    for x in it:
        if x == 'b':
            yield [x] + list(go(it))
        else:
            yield x
            if x == 'c':
                break

to create that irregular list of lists from an iterator.

The inverse of go is just flatten(output_of_go) so the inverse of go(iter(string)) is ''.join(flatten(output_of_go)). You can see that with this test code:

lst = "aaabaabacabaacaca"
assert ''.join(flatten(go(iter(lst)))) == lst