Here's a recursive directory traversal in Python:

  import os
  import os.path
  
  def list_files_recursive(path):
      filenames = os.listdir(path)
      for filename in filenames:
          fullname = os.path.join(path, filename)
          if os.path.isdir(fullname):
              yield from list_files_recursive(fullname) # recursively explore folders
          else:
              yield fullname

and here is the same program with an explicit stack

  import os
  import os.path
  
  def list_files_stack(path):
      folders = [path] # create stack of unexplored folders
      while folders: # repeat until stack is empty
          path = folders.pop() # pick a folder from stack
          filenames = os.listdir(path)
          for filename in filenames:
              fullname = os.path.join(path, filename)
              if os.path.isdir(fullname):
                  folders.append(fullname) # push folder to stack
              else:
                  yield fullname