[python] Is a Python dictionary an example of a hash table?

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?

Yes. Internally it is implemented as open hashing based on a primitive polynomial over Z/2 (source).

There must be more to a Python dictionary than a table lookup on hash(). By brute experimentation I found this hash collision:

>>> hash(1.1)
2040142438
>>> hash(4504.1)
2040142438

Yet it doesn't break the dictionary:

>>> d = { 1.1: 'a', 4504.1: 'b' }
>>> d[1.1]
'a'
>>> d[4504.1]
'b'

Sanity check:

>>> for k,v in d.items(): print(hash(k))
2040142438
2040142438

Possibly there's another lookup level beyond hash() that avoids collisions between dictionary keys. Or maybe dict() uses a different hash.

(By the way, this in Python 2.7.10. Same story in Python 3.4.3 and 3.5.0 with a collision at hash(1.1) == hash(214748749.8).)

To expand upon nosklo's explanation:

a = {}
b = ['some', 'list']
a[b] = 'some' # this won't work
a[tuple(b)] = 'some' # this will, same as a['some', 'list']