python内置函数5-frozenset()
Help on> class frozenset(object)|frozenset() -> empty frozenset object
|frozenset(iterable) -> frozenset object
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|Build an immutable unordered collection of unique elements.
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|Methods defined here:
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|__and__(...)
| x.__and__(y) <==> x&y
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|__cmp__(...)
| x.__cmp__(y) <==> cmp(x,y)
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|__contains__(...)
| x.__contains__(y) <==> y in x.
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|__eq__(...)
| x.__eq__(y) <==> x==y
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|__ge__(...)
| x.__ge__(y) <==> x>=y
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|__getattribute__(...)
| x.__getattribute__('name') <==> x.name
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|__gt__(...)
| x.__gt__(y) <==> x>y
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|__hash__(...)
| x.__hash__() <==> hash(x)
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|__iter__(...)
| x.__iter__() <==> iter(x)
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|__le__(...)
| x.__le__(y) <==> x<=y
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|__len__(...)
| x.__len__() <==> len(x)
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|__lt__(...)
| x.__lt__(y) <==> x<y
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|__ne__(...)
| x.__ne__(y) <==> x!=y
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|__or__(...)
| x.__or__(y) <==> x|y
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|__rand__(...)
| x.__rand__(y) <==> y&x
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|__reduce__(...)
| Return state information for pickling.
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|__repr__(...)
| x.__repr__() <==> repr(x)
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|__ror__(...)
| x.__ror__(y) <==> y|x
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|__rsub__(...)
| x.__rsub__(y) <==> y-x
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|__rxor__(...)
| x.__rxor__(y) <==> y^x
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|__sizeof__(...)
| S.__sizeof__() ->> |
|__sub__(...)
| x.__sub__(y) <==> x-y
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|__xor__(...)
| x.__xor__(y) <==> x^y
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|copy(...)
| Return a shallow copy of a set.
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|difference(...)
| Return the difference of two or more sets as a new set.
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| (i.e. all elements that are in this set but not the others.)
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|intersection(...)
| Return the intersection of two or more sets as a new set.
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| (i.e. elements that are common to all of the sets.)
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|isdisjoint(...)
| Return True if two sets have a null intersection.
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|issubset(...)
| Report whether another set contains this set.
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|issuperset(...)
| Report whether this set contains another set.
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|symmetric_difference(...)
| Return the symmetric difference of two sets as a new set.
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| (i.e. all elements that are in exactly one of the sets.)
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|union(...)
| Return the union of sets as a new set.
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| (i.e. all elements that are in either set.)
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|----------------------------------------------------------------------
|Data and other attributes defined here:
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|__new__ = <built-in method __new__ of type object>
| T.__new__(S, ...) -> a new object with type S, a subtype of T
class frozenset()
Return a new frozenset object, optionally with elements taken from iterable. frozenset is a built-in>
For other containers see the built-in set, list, tuple, and dict> 中文说明：
本函数是返回一个冻结的集合。所谓冻结就是这个集合不能再添加或删除任何集合里的元素。
它是不可变的，存在哈希值，好处是它可以作为字典的key，也可以作为其它集合的元素。缺点是一旦创建便不能更改，没有add，remove方法。
>>> y=
>>> print(len(y),y)
(9, )
>>> set=frozenset(y)
>>> print(len(set),set)
(9, frozenset())
>>> t=frozenset('bookshop')
>>> t
frozenset(['b', 'h', 'k', 'o', 'p', 's'])
>>> t=frozenset('bookshop')
>>> t
frozenset(['b', 'h', 'k', 'o', 'p', 's'])
>>> for i in t:
... print(i)
...
b
h
k
o
p
s
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