Prompt user to enter a filename until it is valid after FileNotFoundError

Question

I'm stuck on this question where after a FileNotFoundError is caught, the user has to enter filenames until they enter a valid filename or Q to quit. I don't know what the valid filenames are so I cant do if filename != valid_filename so I have to do a loop with FileNotFoundError in it but don't know how. Here's what I got so far

def get_file_object(self):
    try:
        input_file = open(self.file_name, 'r')
        words = input_file.read().split("/n")
    except FileNotFoundError:
       print("{} cannot be found.").format(self.file_name)
       new_file_name = input("Please enter a valid file name or Q to quit:")

Does this answer your question? [Asking the user for input until they give a valid response](https://stackoverflow.com/questions/23294658/asking-the-user-for-input-until-they-give-a-valid-response) — Wups, Feb 01 '22 at 09:06

kapebm · Answer 1 · 2022-02-01T11:07:15.553

You could add a flag for example.

def get_file_object(self):
   flag = True
   while flag:
      try:
         input_file = open(self.file_name, 'r')
         words = input_file.read().split("/n")
         flag = False
      except FileNotFoundError:
         print("{} cannot be found.").format(self.file_name)
         self.file_name = input("Please enter a valid file name or Q to quit")
         if self.file_name == "Q":
            print("Quitting...")
            flag = False

score 0 · Answer 2 · answered Feb 01 '22 at 09:16

See the code below. The approach is to repeat the action till the user is making right choice. The comments will give the idea what we are doing. I know this is repetition.

def get_file_object(self):
    is_valid = False
    # Assume we don't have a good file at first
    while not is_valid:
        try:
            # Open the file, if its ok then we are done
            input_file = open(self.file_name, 'r')

            words = input_file.read().split("/n")
            is_valid = True # If we get here we are ok, Quit the loop
            return words # may be??
        except FileNotFoundError:
            # If we get here then the file was not found, then we need to do the cycle again!
            print("{} cannot be found.").format(self.file_name)
            self.file_name = input("Please enter a valid file name or Q to quit")
            # If the user wants to quit, then exit the program by making the flag True
            is_valid = self.file_name == "Q"

Muhammad Mohsin Khan · Answer 3 · 2022-02-01T09:54:16.817

When FileNotFoundError is caught, you can continue the loop until a valid filename is provided. When this is achieved in the try clause, the program will jump to else clause to break the loop. You can do it like this:

def get_file_object(self):
    while True:
        try:
           if self.file_name == "Q":
               print("You have chosen to quit the program.")
               break
           
           input_file = open(self.file_name, 'r')
           words = input_file.read().split("/n")

        except FileNotFoundError:
           print("{} cannot be found.").format(self.file_name)
           self.file_name = input("Please enter a valid file name or Q to quit")
           continue
    
        else:
            break

The loop will also break if the user writes Q as the input.

Prompt user to enter a filename until it is valid after FileNotFoundError

3 Answers3