How to check allowed file extensions in flask

Question

I am working on a code where in I need to define a fuction which checks for the allowed file extensions. The fuction takes filename and extension as arguments as shown below:

def allowed_file(filename, extensions=None):

Steps to write the function:

• extensions' is either None or a list of file extensions.
• If a list is passed as 'extensions' argument, check if 'filename' contains one of the extension provided in the list and return True or False respectively.
• If no list is passed to 'extensions' argument, then check if 'filename' contains one of the extension provided in list
  'ALLOWED_EXTENSIONS', defined in 'config.py',and return True or False respectively.

Kindly guide how to proceed on this.

Answer 1

Since we don't do homework in stackoverflow I'm not going to give you the full code.

But I can give you the pseudo code:

First of all filenames in python are provided in their full form: file1.txt , image.png and so on.

For checking if a list contains an object we use in operator: "txt" in extensions => True

def allowed_extensions(filename,extensions=None):
    # TODO : Extract the file extension from filename
    # TODO : Check if the extension exists in extensions list or not
    # TODO : Return True if it exists and False if not

btw, these links can help you:

in and not operator in python

split function in python