Dictionaries are one of the built in types that I really like in Python. (I think of them as the equivalent of dt and dd in HTML, if that helps anyone.)

But I made a typo, and that typo works. Now the typo is playing with my head. Take a look as this history from the Python Interpreter:

>>> d={} 
>>> d['key']=d
>>> d
{'key': {...}}

Yes, if this is correct, Python knows that dictionary ‘d’ has a key named ‘key’ that contains dictionary ‘d’.

What makes this example particularly cool is the {...}, which shows Python knows that there is no bottom at the end of this dictionary.

This is so cool.

These examples work too:

>>> d['key']['key']
{'key': {...}}
>>> d['key']['key']['key']['key']['key']['key']
{'key': {...}}