PermissionError: [Errno 13] Permission denied: './data/' flask code example

Example: PermissionError: [Errno 13] Permission denied on flask

if__name__=='__main__':
  app.debug=True
  app.run('0.0.0.0', port=5001) #port can be anything higher than 5000.
  
  #this solution is for an OSError and PermissionError
  #Make sure to run it on a virual environment for Flask, Python.