python 集合set的创建，更改，遍历，元算合并，交集，补集

python 集合set的创建，更改，遍历，元算合并，交集，补集

set的创建，set不允许有重复的元素

s = set('cheershopa')        可以修改的set,t = frozenset('bookshopa')   不可须该的setr = set([1,2,3,34,15,25,35,45,75]) 列表转化到sett = {} 空seto = set([]) 空set

set的联合 交集 差补

s | t 求s 与    t的并集  结果和s的类型一样s & t 求 s 与 t的交集，结果是s和类型一样s - t 求 s 与  t 的差补 结果和s的类型一样s.union(t)s.intersection(t)s.difference(t)s.copy()s.superset(t)s.subset(t)s |= ts &= ts -= t

set的内建方法help(set)

>>> help(set) Help on class set in module __builtin__:class set(object) |  set() -> new empty set object |  set(iterable) -> new set object |   |  Build an unordered collection of unique elements. |   |  Methods defined here: |   |  __and__(...) |      x.__and__(y) <==> x&y |   |  __cmp__(...) |      x.__cmp__(y) <==> cmp(x,y) |   |  __contains__(...) |      x.__contains__(y) <==> y in x. |   |  __eq__(...) |      x.__eq__(y) <==> x==y |   |  __ge__(...) |      x.__ge__(y) <==> x>=y |   |  __getattribute__(...) |      x.__getattribute__('name') <==> x.name |   |  __gt__(...) |      x.__gt__(y) <==> x>y |   |  __iand__(...) |      x.__iand__(y) <==> x&=y |   |  __init__(...) |      x.__init__(...) initializes x; see help(type(x)) for signature |   |  __ior__(...) |      x.__ior__(y) <==> x|=y |   |  __isub__(...) |      x.__isub__(y) <==> x-=y |   |  __iter__(...) |      x.__iter__() <==> iter(x) |   |  __ixor__(...) |      x.__ixor__(y) <==> x^=y |   |  __le__(...) |      x.__le__(y) <==> x<=y |   |  __len__(...) |      x.__len__() <==> len(x) |   |  __lt__(...) |      x.__lt__(y) <==> x<y |   |  __ne__(...) |      x.__ne__(y) <==> x!=y |   |  __or__(...) |      x.__or__(y) <==> x|y |   |  __rand__(...) |      x.__rand__(y) <==> y&x |   |  __reduce__(...) |      Return state information for pickling. |   |  __repr__(...) |      x.__repr__() <==> repr(x) |   |  __ror__(...) |      x.__ror__(y) <==> y|x |   |  __rsub__(...) |      x.__rsub__(y) <==> y-x |   |  __rxor__(...) |      x.__rxor__(y) <==> y^x |   |  __sizeof__(...) |      S.__sizeof__() -> size of S in memory, in bytes |   |  __sub__(...) |      x.__sub__(y) <==> x-y |   |  __xor__(...) |      x.__xor__(y) <==> x^y |   |  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. |   |  ---------------------------------------------------------------------- |  Data and other attributes defined here: |   |  __hash__ = None |   |  __new__ = <built-in method __new__ of type object> |      T.__new__(S, ...) -> a new object with type S, a subtype of T