"set" in python

[Humble]

set is an unordered collection of unique elements. Very useful to remove duplicate entries from a collection/sequence/iteratable object.

The elements of a Python set must be immutable. In particular, you can’t have list or dictionary elements in a set.
sets do not support indexing, slicing, or other sequence-like behavior. Values of type set are mutable..

Below methods are available with “sets”..

|  add(...)
 |      Add an element to a set.
 |      
 |      This has no effect if the element is already present.
 |  
 |  clear(...)
 |      Remove all elements from this set.
 |  
 |  copy(...)
 |      Return a shallow copy of a set.
 |  
 |  difference(...)
 |      Return the difference of two or more sets as a new set.
 |      
 |      (i.e. all elements that are in this set but not the others.)
 |  
 |  difference_update(...)
 |      Remove all elements of another set from this set.
 |  
 |  discard(...)
 |      Remove an element from a set if it is a member.
 |      
 |      If the element is not a member, do nothing.
 |  
 |  intersection(...)
 |      Return the intersection of two or more sets as a new set.
 |      
 |      (i.e. elements that are common to all of the sets.)
 |  
 |  intersection_update(...)
 |      Update a set with the intersection of itself and another.
 |  isdisjoint(...)
 |      Return True if two sets have a null intersection.
 |  

 |  issubset(...)
 |      Report whether another set contains this set.
 |  
 |  issuperset(...)
 |      Report whether this set contains another set.
 |  
 |  pop(...)
 |      Remove and return an arbitrary set element.
 |      Raises KeyError if the set is empty.
 |  
 |  remove(...)
 |      Remove an element from a set; it must be a member.
 |      
 |      If the element is not a member, raise a KeyError.
 |  
 |  symmetric_difference(...)
 |      Return the symmetric difference of two sets as a new set.
 |      
 |      (i.e. all elements that are in exactly one of the sets.)
 |  
 |  symmetric_difference_update(...)
 |      Update a set with the symmetric difference of itself and another.
 |  
 |  union(...)
 |      Return the union of sets as a new set.
 |      
 |      (i.e. all elements that are in either set.)
 |  
 |  update(...)
 |      Update a set with the union of itself and others.


Examples:

>>>> s = [1,2,1,2,12,333]
>>> set(s)
set([1, 2, 12, 333])

>>> s1= set(s)
>>> s1
set([1, 2, 12, 333])

>>> type(s1)
<type 'set'>

>>> len(s1)
4
>>> s2=[8,54]
>>> s1.union(s2)
set([1, 2, 8, 12, 333, 54])
>>> s1
set([1, 2, 12, 333])
>>> for x in s1:
...     print x
... 
1
2
12
333
>>> 2 in s1
True
>>> 3 in s1
False


like union others like intersection(), difference(), copy() and symmetric_difference() ..etc are possible on sets..

 s1|set(s2)
set([1, 2, 54, 8, 12, 333])
>>> s1
set([1, 2, 12, 333])
>>> s2
[8, 54]
>>> s1&set(s2)
set([])
>>> 

>>> s1.add(100)
>>> s1
set([1, 2, 12, 333, 100])
>>> 

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