directory_diving

def flatten(li):
    flat_li = []
    for e in li:
        if isinstance(e, list):
            flat_li += flatten(e)
        else:
            flat_li.append(e)
    return flat_li

def ndeep(folder, n):
    files = []
    if n == 0:
        return folder
    for file in folder:
        if isinstance(file, list):
            files += ndeep(file, n-1)
    return flatten(files)

# folder = ['a', ['b'], ['c', [['d'], 'e']]]
# n = 3
# print(ndeep(folder, n))