dict and __cmp__() question

[Alex]

Entering

>>> help(dict)
Help on class dict in module __builtin__:

class dict(object)
 |  dict() -> new empty dictionary.
 |  dict(mapping) -> new dictionary initialized from a mapping object's
 |      (key, value) pairs.
 |  dict(seq) -> new dictionary initialized as if via:
 |      d = {}
 |      for k, v in seq:
 |          d[k] = v
 |  dict(**kwargs) -> new dictionary initialized with the name=value
pairs
 |      in the keyword argument list.  For example:  dict(one=1, two=2)
 |
 |  Methods defined here:
 |
 |  __cmp__(...)
 |      x.__cmp__(y) <==> cmp(x,y)
 |
 |  __contains__(...)
 |      D.__contains__(k) -> True if D has a key k, else False

snip

 |  update(...)
 |      D.update(E, **F) -> None.  Update D from E and F: for k in E:
D[k] = E[k]
 |      (if E has keys else: for (k, v) in E: D[k] = v) then: for k in
F: D[k] = F[k]
 |
 |  values(...)
 |      D.values() -> list of D's values

Now I understand methods like update(...) and values(...), for instance

>>> D={'a':1, 'b':2}
>>> D.values()
[1, 2]
>>>

But what are those with double underscore? For instance __cmp__(...)?

I tried
>>> D.cmp('a','b')

Traceback (most recent call last):
  File "<pyshell#7>", line 1, in -toplevel-
    D.cmp('a','b')
AttributeError: 'dict' object has no attribute 'cmp'
>>>

Alex