Convert a python non-tail recursive function adding sub-folders info to a loop

Question

I wrote a function to get the total size and total files/subdirs of the entire disk or specific folder. The recursive function was very simple:

# Make the python dirSize function a non recursive one:
from pathlib import Path

obj = {}
def dirSize(dir: Path, size = 0, files = 0, dirs = 0):
    for sub_dir in dir.glob('*'):
        if sub_dir.is_dir():
            dirs += 1
            res_size, res_files, res_dirs = dirSize(sub_dir)
            size += res_size
            files += res_files
            dirs += res_dirs
        elif sub_dir.is_file():
            files += 1
            size += sub_dir.stat().st_size
    
    obj[dir.as_posix()] = {
        'size': size,
        'files': files,
        'dirs': dirs,
    }
    
    return size, files, dirs

dirSize(Path('~/Documents').expanduser())
#Line above is for tests. Final code should run in elevated cmd:
#dirSize(Path('C:/'))

with open(Path('~/Desktop/results.tsv').expanduser().as_posix(), 'w') as file:
    file.write('Directory\tBytes\tFiles\tDirs\n')
    for key in sorted(obj):
        dir = obj[key]
        file.write(key)
        file.write('\t')
        file.write(str(dir['size']))
        file.write('\t')
        file.write(str(dir['files']))
        file.write('\t')
        file.write(str(dir['dirs']))
        file.write('\n')

I tried to use AI to convert it to a non recursive function, but AI seems to ignore these lines are a bottom up sum, not a simple sum:

size += res_size
files += res_files
dirs += res_dirs

So I tried a stack loop, like in the Dijkstra algorithm, but it turns up that I couldn't find a simple solution to make the bottom up sum. Alternatively I could add level/parent/child properties to the obj variable to make a bottom up sum after the queue processing. But this seems very cumbersome. Is there a simpler way to achieve this?

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Replying questions asked below:

1. Why don't you just use os.walk?

• It eliminates the recursion immediately, but doesn't help to do the bottom up sum - the generated report shows how many subdirs, disk space and files each directory has.

2. What's the problem with the recursive function?

• There is no problem, it works to perfection! But my boss thinks not all developers can work with recursion, so he asked me for a non recursive version and I'm struggling to not make it too complicated.

Answer 1

Based on answer from @awarrier99 I came up with this version that simplifies the logic a bit. I hope this helps future researchers:

def dirSizeIterative(dir: Path):
    dirs = [(dir, {'size': 0, 'files': 0, 'dirs': 0}, None)]
    i = 0

    #step 1, read dir/files info and add to array
    while i < len(dirs):
        dir, info, _ = dirs[i]
        i += 1
        
        for sub_dir in dir.glob('*'):
            if sub_dir.is_dir():
                info['dirs'] += 1
                dirs.append((sub_dir, {'size': 0, 'files': 0, 'dirs': 0}, info))
            elif sub_dir.is_file():
                info['files'] += 1
                info['size'] += sub_dir.stat().st_size

    #step 2, bottom up sum using the parent
    for _, info, parent in dirs[-1:0:-1]:
        parent['size'] += info['size']
        parent['files'] += info['files']
        parent['dirs'] += info['dirs']
    
    return {dir.as_posix(): info for dir, info, _ in dirs}