Return files only from specific folder

Question

Hello.

I wrote a function in Python, that must return file from specific folder and all subfolders. File name taken from function parameter:

def ReturnFile(fileName)
  return open("C:\\folder\\" + fileName,"r")

But as fileName you can pass for example: "..\\Windows\\passwords.txt" or some unicode symbols for dots.

How to fix it? Some RegExp maybe?

Answer 1

The os.path.normpath function normalizes a given path py resolving things like "..". Then you can check if the resulting path is in the expected directory:

def ReturnFile(fileName)
  norm = os.path.abspath("C:\\folder\\" + fileName)
  if not norm.startswith("C:\\folder\\"):
    raise Exception("Invalid filename specified")
  return open(norm,"r")

Answer 2

How about this:

import os

_BASE_PATH= "C:\\folder\\"

def return_file(file_name):
    "Return File Object from Base Path named `file_name`"
    os.path.normpath(file_name).split(os.path.sep)[-1]
    return(open(_BASE_PATH+file_name))