list of entries (files and folders) in a directory tree by os.scandir() in Python

Question

I have used "os.walk()" to list all subfolders and files in a directory tree , but heard that "os.scandir()" does the job up to 2X - 20X faster. So I tried this code:

def tree2list (directory:str) -> list:
    import os
    tree = []
    counter = 0
    for i in os.scandir(directory):
        if i.is_dir():
            counter+=1
            tree.append ([counter,'Folder', i.name, i.path])  ## doesn't list the whole tree
            tree2list(i.path)
            #print(i.path)  ## this line prints all subfolders in the tree
        else:
            counter+=1
            tree.append([counter,'File', i.name, i.path])
            #print(i.path)  ## this line prints all files in the tree
    return tree

and when test it:

    ## tester
folder = 'E:/Test'
print(tree2list(folder))

I got only the content of the root directory and none from sub-directories below tree hierarchy, while all print statements in above code work fine.

[[1, 'Folder', 'Archive', 'E:/Test\\Archive'], [2, 'Folder', 'Source', 'E:/Test\\Source']]

What have I done wrong ?, and how can I fix it?!

Answer 1

Your code almost works, just a minor modification is required:

def tree2list(directory: str) -> list:
    import os
    tree = []
    counter = 0
    for i in os.scandir(directory):
        if i.is_dir():
            counter += 1
            tree.append([counter, 'Folder', i.name, i.path])
            tree.extend(tree2list(i.path))
            # print(i.path)  ## this line prints all subfolders in the tree
        else:
            counter += 1
            tree.append([counter, 'File', i.name, i.path])
            # print(i.path)  ## this line prints all files in the tree
    return tree

Although I don't understand what the purpose of the counter variable is, so I'd probably remove it.

Further, I have to agree with @Gelineau that your approach utilizes array-copies quite heavily and is therefore most likely quite slow. An iterator based approach as in his response is more suited for a large number of files.

Answer 2

Using generators (yield, yield from) allows to manage the recursion with concise code:

from pprint import pprint
from typing import Iterator, Tuple


def tree2list(directory: str) -> Iterator[Tuple[str, str, str]]:
    import os

    for i in os.scandir(directory):
        if i.is_dir():
            yield ["Folder", i.name, i.path]
            yield from tree2list(i.path)
        else:
            yield ["File", i.name, i.path]


folder = "/home/yfgy6415/dev/tmp"
pprint(list(tree2list(folder)))

Or: pprint(list(enumerate(tree2list(folder), start=1))) if you want the counter.

Answer 3

Adding to the accepted answer. In case... Getting all files in the directory and subdirectories matching some pattern (*.py for example):

import os
from fnmatch import fnmatch


def file_tree_fn(root):
    file_list = []
    for python_file in os.scandir(str(root)):
        if python_file.is_dir():
            file_list.extend(file_tree_fn(python_file.path))
        else:
            file_list.append(python_file.path) if fnmatch(python_file.path, "*.py") & python_file.is_file() else None
    return file_list

print(file_tree_fn(root))