<p>One of the basic data structures in Python is the dictionary, which allows one to record "keys" for looking up "values" of any type.  Is this implemented internally as a hash table?  If not, what is it?</p>

Yes, it is a hash mapping or hash table. You can read a description of python's dict implementation, as written by Tim Peters,
here
.
That's why you can't use something 'not hashable' as a dict key, like a list:
```
```
>>> a = {}
>>> b = ['some', 'list']
>>> hash(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list objects are unhashable
>>> a[b] = 'some'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list objects are unhashable
```
```
You can
read more about hash tables
or
check how it has been implemented in python
and
why it is implemented that way
.