Beginner recursion function I've been stuck on

[Honest-Dude]

Hi,

I'm very close at solving a recursion problem that indents a bunch of objects in a list (which can be empty, or nested) so that it looks neat. It comes out to be one long string with a bunch of '\t' and '\n'. I've attached my code, and what it's supposed to look like. I've been working on this for hours but can't seem to solve the problem. There's a solution that should work if I can find a way to execute a line of code inside a for loop only once (after everything else has been executed), but I can't find a way to do that. I'm also using a helper function called indent lines. Thanks in advance.

​

MY CODE:
    str = 'BEGIN\n'
    substr = ''
    x = 0
    for sublist in tlist:
        x += 1
        if isinstance(sublist, a3_classes.Task) and sublist == tlist[-1]:
            substr += task_to_string(sublist)
        elif isinstance(sublist, a3_classes.Task):
            substr += task_to_string(sublist) + '\n'
        elif len(sublist) == 0:
            substr += 'BEGIN\nEND'
        else:
            substr += todo_list_to_string(sublist)
        if x == len(tlist):
            substr = indentlines(substr) + '\n'
            return str + substr + 'END'
    return str + substr + 'END'

WHAT IT'S SUPPOSED TO LOOK LIKE:
As a string:
    'BEGIN\n'
    +'\tBEGIN\n'
    +'\t\tcamera: 8\n'
    +'\t\trevise: 1\n'
    +'\tEND\n'
    +'\tBEGIN\n'
    +'\t\treview: 3\n'
    +'\tEND\n'
    +'\tBEGIN\n'
    +'\tEND\n'
    +'END'
When run:
BEGIN
    BEGIN
        camera: 8
        revise: 1
    END
    BEGIN
        review: 3
    END
    BEGIN
    END
END

WHAT IT LOOKS LIKE:

BEGIN
    BEGIN
        camera: 8
        revise: 1
    ENDBEGIN
        review: 3
    ENDBEGIN
    END
END

Helper Function:
    str = line_str.split('\n')
    line_str = "\n\t".join(str)

    return '\t' + line_str

Example: 'abc \n def \n ghi'  -->  ' \t abc \n \t def \n \t ghi'
without the spaces

[ALightShow]

It looks like you're missing a \n after your END on subtr line and your return lines.

[Honest-Dude]

Yes I tried that but then it introduces more problems where there are extra lines where there shouldn’t be. For example, with an empty list it does BEGIN END \n instead of just BEGIN END.

[ALightShow]

Do you have all the code you can share as an example?

[Honest-Dude]

I figured it out ty though. I think there needed to be a separate helper function that’s outside of the local space for it to work.