Python 集合方法总结

1、添加一个元素：
    add(...)

       Addan element to a set.

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>>> a = {'shaw',11,22} >>>a.add('sina') >>> a {'sina', 11, 22,'shaw'}

2、清空集合

    clear(...)

       Remove all elements from this set.

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>>> a = {'shaw',11,22} >>>a.clear() >>> a set()

3、浅copy

    copy(...)

      Return a shallow copy of a set.

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>>> a = {'shaw',11,22} >>> b =a.copy() >>>print(b) {11, 22, 'shaw'}

4、返回一个A中存在，B中不存在元素的集合

    difference(...)

      Return the difference of two or more setsas a new set.

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>>> A = {'shaw',11,22} >>> B ={11,"sam"} >>>A.difference(B) {22, 'shaw'}

5、从当前元素中删除和B中相同的元素

    difference_update(...)

      Remove all elements of another set fromthis set.

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>>> A = {'shaw',11,22} >>> B ={11,"sam"} >>>A.difference_update(B) >>>print(A) {22, 'shaw'}

6、删除指定元素，如果不存在不会报错

    discard(...)

      Remove an element from a set if it is amember.

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>>> A = {'shaw',11,22} >>>A.discard(11) >>>print(A) {22, 'shaw'} >>>A.discard(15) >>>print(A) {22, 'shaw'}

7、取交集

    intersection(...)

      Return the intersection of two sets as anew set.

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>>> a = {'shaw',11,22} >>> b ={'sam',22} >>>a.intersection(b) {22}

8、取交集，并更新到A中

    intersection_update(...)

      Update a set with the intersection ofitself and another.

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>>> A = {'shaw',11,22} >>> B ={'sam',22} >>>A.intersection_update(B) >>> print(A) {22}

9、判断是否有交集，如果没有交集，返回True，否则返回False

    isdisjoint(...)

      Return True if two sets have a nullintersection.

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>>> A = {'shaw',11,22} >>> B ={'sam',22} >>>A.isdisjoint(B) False

10、判断是否是子序列

    issubset(...)

      Report whether another set contains thisset.

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>>> A = {'shaw',11,22} >>> B ={'sam',22} >>>B.issubset(A) False >>> C ={'shaw'} >>>C.issubset(A) True

11、判断是否是父序列

    issuperset(...)

      Report whether this set contains anotherset.

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>>> A = {'shaw',11,22} >>> B ={22} >>>A.issuperset(B) True

12、移除元素，如果集合为空，会报错

    pop(...)

      Remove and return an arbitrary setelement.

      Raises KeyError if the set is empty.

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>>> A = {'shaw',11,1,98,3,'abc','Shaw'} >>>A.pop() 1 >>>print(A) {98, 3, 'abc', 11,'Shaw', 'shaw'}

13、删除指定元素，元素不存在会报错

    remove(...)

      Remove an element from a set; it must be amember.

      If the element is not a member, raise aKeyError.

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>>> A = {'shaw',11,22,1,98,3,'abc','Shaw'} >>>A.remove('22') Traceback (mostrecent call last):    File "<input>", line 1, in<module> KeyError: '22' >>>A.remove(22) >>>print(A) {1, 98, 3, 'abc',11, 'Shaw', 'shaw'}

14、取并集

    union(...)

      Return the union of sets as a new set.

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>>> A = {'shaw',11,22,1,98,3,'abc','Shaw'} >>> B ={11,'sam'} >>>A.union(B) {'sam', 1, 98, 3,'abc', 11, 'Shaw', 22, 'shaw'}

15、对称差集

    symmetric_difference(...)

      Return the symmetric difference of twosets as a new set.

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>>> A = {'shaw',11,22,1,98,3,'abc','Shaw'} >>> B ={11,'sam'} >>>A.symmetric_difference(B) {'sam', 1, 98, 3,'abc', 'Shaw', 22, 'shaw'}

16、更新

    update(...)

      Update a set with the union of itself andothers.

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>>> A = {'shaw',11,22,1,98,3,'abc','Shaw'} >>> B ={11,'sam'} >>>A.update(B) >>>print(A) {'sam', 1, 98, 3,'abc', 11, 'Shaw', 22, 'shaw'}