Python 集合 set
python set 集合
set 集合是一种数据类型
set跟list一样可以用{}来定义，但是pyton -v 版本 >2.7
set的数据格式：
s1={"abc","def"} #{} 自己定义
>>> print s1
set(['abc', 'def'])
>>> s2=set("abcdef") #set 函数用string进行初始化
>>> print s2
set(['a', 'c', 'b', 'e', 'd', 'f'])
>>> s3=set(["abc",123,"def"]) #set 函数用list进行初始化
>>> print s3
set([123, 'abc', 'def'])
结合set的基本方法
| add(...) #set 后面追加一个element
| Add an element to a set.
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| This has no effect if the element is already present.
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| clear(...)
| Remove all elements from this set.
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| copy(...)
| Return a shallow copy of a set.
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| difference(...) #s3.difference(s4) #s3 跟s4 不同的element 组成一个新的set
| 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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| difference_update(...)
| Remove all elements of another set from this set.
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>>> print s4
set(['abc', 'def', 'ghk'])
>>> s3={"abc",123,"def"}
>>> s3.difference(s4) #之前的s3 s4 都不变，会把s3 中有，s4中没有的数据打印出来组成一个新的set
set([123])
>>> print s3
set([123, 'abc', 'def'])
>>> print s4
set(['abc', 'def', 'ghk'])
>>> s3.difference_update(s4) #s3 直接是上面的结果，s4 不变化
>>> print s3
set([123])
>>> print s4
set(['abc', 'def', 'ghk'])
| discard(...)
| Remove an element from a set if it is a member.
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| If the element is not a member, do nothing.
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| intersection(...) #交集
| 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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| intersection_update(...)
| Update a set with the intersection of itself and another.
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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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| pop(...)
| Remove and return an arbitrary set element.
| Raises KeyError if the set is empty.
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| remove(...)
| Remove an element from a set; it must be a member.
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| If the element is not a member, raise a KeyError.