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python set
set是一个工厂函数(filter也是工厂函数),是一个可变的集合
frozenset 不可变的集合,与set共性,他也在内部自动去重,
1 >>> num5=frozenset([1,1,1,2,3,]) 2 >>> num5 3 frozenset([1, 2, 3]) 4 >>>
>>> num1=[1,2,3,4,5,5,4,3] >>> tmp=[] >>> for each in num1: if each not in tmp: tmp. SyntaxError: invalid syntax >>> for each int num1: SyntaxError: invalid syntax >>> for each in num1: if each not in tmp: tmp.append(each) >>> num1 [1, 2, 3, 4, 5, 5, 4, 3] >>> tmp [1, 2, 3, 4, 5] >>> num2=list(set(num1)) >>> num1 [1, 2, 3, 4, 5, 5, 4, 3] >>> num2 [1, 2, 3, 4, 5] >>> num3={1,2,3,4} >>> type(num3) <type ‘set‘> >>> >>> 1 in num3 True >>> 7 in num3 False >>> num3.add(6) >>> num3 set([1, 2, 3, 4, 6]) >>> num3.remove(1) >>> num3 set([2, 3, 4, 6]) >>> num3.remove(4) >>> num3 set([2, 3, 6]) >>> >>> >>> num4=frozenst([1,2,3]) Traceback (most recent call last): File "<pyshell#168>", line 1, in <module> num4=frozenst([1,2,3]) NameError: name ‘frozenst‘ is not defined >>> num4=frozenset([1,2,3]) >>> num4 frozenset([1, 2, 3]) >>> type(num4) <type ‘frozenset‘> >>> num4[0] Traceback (most recent call last): File "<pyshell#172>", line 1, in <module> num4[0] TypeError: ‘frozenset‘ object does not support indexing >>> 1 in num4 True >>> 4 not in num4 True >>> 4 in num4 False >>> num4.add(1) Traceback (most recent call last): File "<pyshell#176>", line 1, in <module> num4.add(1) AttributeError: ‘frozenset‘ object has no attribute ‘add‘ >>> help(frozenset) Help on class frozenset in module __builtin__: class frozenset(object) | frozenset() -> empty frozenset object | frozenset(iterable) -> frozenset object | | Build an immutable 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 | | __hash__(...) | x.__hash__() <==> hash(x) | | __iter__(...) | x.__iter__() <==> iter(x) | | __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 | | 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.) | | intersection(...) | Return the intersection of two or more sets as a new set. | | (i.e. elements that are common to all of the sets.) | | 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. | | 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.) | | union(...) | Return the union of sets as a new set. | | (i.e. all elements that are in either set.) | | ---------------------------------------------------------------------- | Data and other attributes defined here: | | __new__ = <built-in method __new__ of type object> | T.__new__(S, ...) -> a new object with type S, a subtype of T >>>
python set
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