📖 Reading Python Error Messages

Suppose you see this.

TypeError: 'NoneType' object is not iterable

Instead of guessing, break it down.

TypeError → You're performing an operation on an incompatible type.
NoneType → The value is None.
not iterable → Python expected something it could loop over, like a list or tuple.

A common cause:

def get_users():
    print("Loading users...")

for user in get_users():
    print(user)


get_users() doesn't return anything, so it returns None by default. Python can't loop over None.

When you see this error, ask yourself:
"Which variable was supposed to contain a list but ended up being None?"