I'm trying to place dictionaries inside a larger dictionary to create a log in system

```
if(os.path.exists('Users.dat')):  
    with open('Users.dat','rb')as f:        
        Users = pickle.load(f)
        f.close()
done=False
while not(done):
    userin = input('Username: ')
    passin = input('Password: ')
    if userin in dict:
        usernames = Users[userin]['Username']
        passwords = Users[userin]['Password']
    else:
        break

```

when i do this it returns this:

```
Username: JTomkins12
Password: 4621
Traceback (most recent call last):
  File "C:\Users\james\Lessons\Computing\Aptana Studio Workspace\Full
Program\FullProgram.py", line 274, in <module>
    loginmenu(choice)
  File "C:\Users\james\Lessons\Computing\Aptana Studio Workspace\Full
Program\FullProgram.py", line 255, in loginmenu
    if userin in dict:
TypeError: argument of type 'type' is not iterable

```

can somebody help me fix this please?