Python: 'NoneType' object is not subscriptable' error [duplicate]

Answer 1

Your select Username query is returning no rows. So the result set is empty and there is nothing to fetch. So your fetchone call returns None instead of the row tuple you expect.

Answer 2

When tyour query return 0 rows fetchone will return None:

usernameSql = """SELECT Username FROM Details WHERE Password = '%s'""" % (passwordAttempt) # Selecting username in database
cur.execute(usernameSql)
usernameSql = cur.fetchone()
# check if the query return at least one record
if usernameSql:
    userFetched = usernameSql[0] 
else:
   # show a error or somthing