一、set集合的特性
- 访问速度快
- 天生解决重复问题
二、set变量申明
- s1 = set()
- s2 = set([1,2,3])
备注：第二种方式在set类中直接传入一个序列。
三、set类中方法大全
1.add函数：
def add(self, *args, **kwargs): # real signature unknown
'''--向一个set集合中添加一个元素--'''
"""
Add an element to a set.
This has no effect if the element is already present.
"""
add
例:
>>> s1 = set()
>>> s1.add(1)
>>> s1
{1}
2.clear函数：
def clear(self, *args, **kwargs): # real signature unknown
'''--清除set集合中的所有元素--'''
""" Remove all elements from this set. """
pass
clear
例：
>>> s1 = set([1,2,3])
>>> s1
{1, 2, 3}
>>> s1.clear()
>>> s1
set()
3.copy函数：
def copy(self, *args, **kwargs): # real signature unknown
'''--返回一个浅拷贝的set集合--'''
""" Return a shallow copy of a set. """
pass
copy
例：
pass
4.difference函数：
def difference(self, *args, **kwargs): # real signature unknown
'''--比较两个set集合得到一个差集--'''
"""
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.)
"""
pass
difference
例：
>>> s1 = set(['one','two','three'])
>>> s2 = s1.difference(['one','two'])
>>> s2
{'three'}
5.difference_update函数：
def difference_update(self, *args, **kwargs): # real signature unknown
'''-新set集合与原来set相比较，从原来set集合中删除新set集合中存在的元素-'''
""" Remove all elements of another set from this set. """
pass
difference_update
例：
>>> s1 = set(['one','two','three'])
>>> s1.difference_update(['one','three'])
>>> s1
{'two'}
6.discard函数：
def discard(self, *args, **kwargs): # real signature unknown
'''-指定删除set集合中的某个元素,如果指定元素不在set集合中，则返回一个none-'''
"""
Remove an element from a set if it is a member.
If the element is not a member, do nothing.
"""
pass
discard
例：
①指定元素存在set集合中：
>>> s1 = set(['one','two','three'])
>>> s1.discard('one')
>>> s1
{'three', 'two'}
②指定元素不存在集合中：
>>> s1 = set(['one','two','three'])
>>> a=s1.discard('four')
>>> print(a)
None
7.intersection函数：
def intersection(self, *args, **kwargs): # real signature unknown
'''--返回两个set集合交集--'''
"""
Return the intersection of two sets as a new set.
(i.e. all elements that are in both sets.)
"""
pass
intersection
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','three'])
>>> s3 = s1.intersection(s2)
>>> s3
{'one', 'three'}
8.intersection_update函数：
def intersection_update(self, *args, **kwargs): # real signature unknown
'''--将老set集合的值更新为新set集合与老set集合交集--''
""" Update a set with the intersection of itself and another. """
pass
intersection_update
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','three'])
>>> s1.intersection_update(s2)
>>> s1
{'one', 'three'}
9.isdisjoint函数：
def isdisjoint(self, *args, **kwargs): # real signature unknown
'''--如果两个set集合没有交集，返回True--'''
""" Return True if two sets have a null intersection. """
pass
isdisjoint
例：
①没有交集：
>>> s1 = set(['one','two','three'])
>>> s2 = set([1,2,3])
>>> s1.isdisjoint(s2)
True
②有交集：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one'])
>>> s1.isdisjoint(s2)
False
10.issubset函数：
def issubset(self, *args, **kwargs): # real signature unknown
'''--判断当前这个set集合是否是另一个set集合的子集--'''
""" Report whether another set contains this set. """
pass
issubset
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one'])
>>> s2.issubset(s1) #是子集的情况
True
>>> s1.issubset(s2) #不是子集的情况
False
11.issuperset函数：
def issuperset(self, *args, **kwargs): # real signature unknown
'''--判断当前这个set集合是否是另外一个set集合父集--'''
""" Report whether this set contains another set. """
pass
issuperset
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one'])
>>> s1.issuperset(s2) #s1是s2的父集情况
True
>>> s2.issuperset(s1) #s2不是s1父集的情况
False
12.pop函数：
def pop(self, *args, **kwargs): # real signature unknown
'''--随机删除set集合中的元素，并且返回被删除的元素--'''
"""
Remove and return an arbitrary set element.
Raises KeyError if the set is empty.
"""
pass
pop
例：
>>> s1 = set(['one','two','three'])
>>> s1.pop()
'one'
>>> s1
{'three', 'two'}
13.remove函数：
def remove(self, *args, **kwargs): # real signature unknown
'''--指定删除set集合中的元素--'''
"""
Remove an element from a set; it must be a member.
If the element is not a member, raise a KeyError.
"""
pass
remove
例：
>>> s1 = set(['one','two','three'])
>>> s1.remove("one")
>>> s1
{'three', 'two'}
14.symmetric_difference函数：
def symmetric_difference(self, *args, **kwargs): # real signature unknown
'''--两个set集合的对称集--'''
"""
Return the symmetric difference of two sets as a new set.
(i.e. all elements that are in exactly one of the sets.)
"""
pass
symmetric_difference
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s3 = s1.symmetric_difference(s2)
>>> print(s3)
{'three', 'four'}
15.symmertric_difference_update函数：
def symmetric_difference_update(self, *args, **kwargs):
'''--把两个set集合的交集之外的值，更新替换当前set集合--'''
""" Update a set with the symmetric difference of itself and another. """
pass
symmetric_difference_update
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s1.symmetric_difference_update(s2)
>>> print(s1)
{'three', 'four'}
16.union函数：
def union(self, *args, **kwargs): # real signature unknown
'''--sets集合的并集赋值给一个新的set集合--'''
"""
Return the union of sets as a new set.
(i.e. all elements that are in either set.)
"""
pass
union
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s3=s1.union(s2)
>>> print(s3)
{'one', 'three', 'four', 'two'}
17.update函数：
def update(self, *args, **kwargs): # real signature unknown
'''--更新一个set集合，更新的set集合的值是当前集合和其他集合的并集--'''
""" Update a set with the union of itself and others. """
pass
update
例：
>>> s1 = set(['one','two','three'])
>>> s2 = set(['one','two','four'])
>>> s1.update(s2)
>>> print(s1)
{'three', 'two', 'four', 'one'}
三、总结
1.函数中有带update的函数，或者本身就是update函数，是更新这个set集合本身，并不会将得到的结果重新赋值给一个变量。
2.函数一些函数不带update的函数，如：difference（取不同），intersection（取交集），symmetric_difference（取交集之外的值），union（取并集）等，将得到的结果返回给一个变量。