>>> hash("dsfdfasd")
4008608082288030192
>>> hash("dsfdfase")
-2996068020242219814
>>> hash((1,2,3))
529344067295497451
>>> hash([1,2,3])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
>>> # mutable objects are not hashable
>>> 
>>> s = set()
>>> s
set()
>>> len(s)
0
>>> s.add("a")
>>> s
{'a'}
>>> s.add(True)
>>> s
{True, 'a'}
>>> print(s.add("b"))
None
>>> s
{True, 'a', 'b'}
>>> s.add("b")
>>> s
{True, 'a', 'b'}
>>> # sets do noot ahve duplicates, per ==
>>> # no control over order in which items are presented
>>> "b" in s
True
>>> "quack" in s
False
>>> s = {"a", "b", "c", "e", "m"}
>>> t = {"b", "e", "n", "p", "r"}
>>> s
{'c', 'e', 'b', 'm', 'a'}
>>> t
{'p', 'r', 'e', 'b', 'n'}
>>> s & t
{'e', 'b'}
>>> s.intersection(t)
{'e', 'b'}
>>> s & t
{'e', 'b'}
>>> s.intersection(t)
{'e', 'b'}
>>> s | t
{'c', 'b', 'm', 'a', 'n', 'p', 'r', 'e'}
>>> s.union(t)
{'c', 'b', 'm', 'a', 'n', 'p', 'r', 'e'}
>>> ## union is combined memembershiip of A and B.
>>> s - t
{'m', 'c', 'a'}
>>> s
{'c', 'e', 'b', 'm', 'a'}
>>> t
{'p', 'r', 'e', 'b', 'n'}
>>> s.difference(t)
{'m', 'c', 'a'}
>>> ## relative complement
>>> s ^ t
{'p', 'r', 'c', 'n', 'a', 'm'}
>>> s
{'c', 'e', 'b', 'm', 'a'}
>>> t
{'p', 'r', 'e', 'b', 'n'}
>>> (s | t) - (s & t)
{'c', 'm', 'a', 'n', 'p', 'r'}
>>> s.add([1,2,3])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
>>> #  A and B are disjoint if they have an empty intersection
>>> s.isdisjoint(t)
False
>>> s & t
{'e', 'b'}
>>> s < t
False
>>> t < s
False
>>> s == t
False
>>> #  s <= t means every element of s belongs to t.
>>> # s is a subset of t
>>> # s < t means every element of s belongs to t but s != t
>>> s.discard("e")
>>> s
{'c', 'b', 'm', 'a'}
>>> s.discard("b")
>>> s
{'c', 'm', 'a'}
>>> s.isdisjoint(t)
True
>>> hash(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'set'
>>> d = {}
>>> d["morrison"] = "computer scince"
>>> d["teague"] = "mathematics"
>>> d["vazquez"] = "mathemtics"
>>> 
>>> d["vazquez"] = "mathematics"
>>> d
{'morrison': 'computer scince', 'teague': 'mathematics', 'vazquez': 'mathematics'}
>>> d.keys()
dict_keys(['morrison', 'teague', 'vazquez'])
>>> list(d.keys())
['morrison', 'teague', 'vazquez']
>>> list(d.values())
['computer scince', 'mathematics', 'mathematics']
>>> for k in d.keys(): print(k)
... 
morrison
teague
vazquez
>>> for k in d.keys(): print(d[k])
... 
computer scince
mathematics
mathematics
>>> # keys in dictionaries must be hashable
>>> # elements of sets must be hashable.
>>> # hashing makes these structures highly efficient.
>>> 
>>> #worker statment
>>> # grammatically complete sentence.
>>> #  boss steament is grammatically incomplete
>>> #  can alter the flow of executions.
>>> #  As of now our progams run in seriatum.
>>> quit()