基础数据类型-set

Set是无序不重复元素的序列，基本功能是删除重复元素和测试成员关系，

创建一个集合可以用set()或者({}),但是创建一个空集合只能用set():

s1 = set()
print("s1 is", type(s1))
s2 = ({1, 2, 3})
print("s2 is ", type(s2))
s3 = ({})
print("s3 is", type(s3))

s1 is <class 'set'>
s2 is  <class 'set'>
s3 is <class 'dict'>

功能，删除序列里重复元素，测试成员关系，集合运算：

#删除序列里重复元素
fruits1 = set({"Apple", "Orange", "Pear", "Apple"})
print("fruits1:", fruits1)

#成员测试
if 'Pear' in fruits1:
    print("Pear is in set")
else:
    print("Pear is not in set")

#成员运算
fruits2 = set({"Apple", "Banana", "Strawberry"})
print(fruits1 - fruits2) #在fruits1中但不再fruits2中
print(fruits1 | fruits2) #在fruits1或fruits2中
print(fruits1 & fruits2) #在fruits1且在fruits2中
print(fruits1 ^ fruits2) #在fruits1或fruits2中，但不同时在两个集合中

fruits1: {'Apple', 'Orange', 'Pear'}
Pear is in set
{'Orange', 'Pear'}
{'Apple', 'Orange', 'Strawberry', 'Banana', 'Pear'}
{'Apple'}
{'Strawberry', 'Banana', 'Orange', 'Pear'}

Set常用方法有add(), difference(),intersection()等:

#set常用方法
fruits2.add("Watermelon")
print("fruits2:", fruits2)
print("Fruits in fruits2 but not in fruits1 are:", fruits2.difference(fruits1)) #fruits2中有fruits1中没有
print("Fruits in fruits1 but not in fruits2 are:", fruits1.difference(fruits2)) #fruits1中有fruits2中没有
print("Fruits in fruits1 and fruits2 are:", fruits2.intersection(fruits1)) #fruits1,fruits2的交集

fruits2: {'Strawberry', 'Banana', 'Apple', 'Watermelon'}
Fruits in fruits2 but not in fruits1 are: {'Strawberry', 'Banana', 'Watermelon'}
Fruits in fruits1 but not in fruits2 are: {'Pear', 'Orange'}
Fruits in fruits1 and fruits2 are: {'Apple'}

Set类的定义-其他不常用方法查询：

class set(object):
    """
    set() -> new empty set object
    set(iterable) -> new set object
    
    Build an unordered collection of unique elements.
    """
    def add(self, *args, **kwargs): # real signature unknown
        """
        Add an element to a set.
        
        This has no effect if the element is already present.
        """
        pass

    def clear(self, *args, **kwargs): # real signature unknown
        """ Remove all elements from this set. """
        pass

    def copy(self, *args, **kwargs): # real signature unknown
        """ Return a shallow copy of a set. """
        pass

    def difference(self, *args, **kwargs): # real signature unknown
        """
        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

    def difference_update(self, *args, **kwargs): # real signature unknown
        """ Remove all elements of another set from this set. """
        pass

    def discard(self, *args, **kwargs): # real signature unknown
        """
        Remove an element from a set if it is a member.
        
        If the element is not a member, do nothing.
        """
        pass

    def intersection(self, *args, **kwargs): # real signature unknown
        """
        Return the intersection of two sets as a new set.
        
        (i.e. all elements that are in both sets.)
        """
        pass

    def intersection_update(self, *args, **kwargs): # real signature unknown
        """ Update a set with the intersection of itself and another. """
        pass

    def isdisjoint(self, *args, **kwargs): # real signature unknown
        """ Return True if two sets have a null intersection. """
        pass

    def issubset(self, *args, **kwargs): # real signature unknown
        """ Report whether another set contains this set. """
        pass

    def issuperset(self, *args, **kwargs): # real signature unknown
        """ Report whether this set contains another set. """
        pass

    def pop(self, *args, **kwargs): # real signature unknown
        """
        Remove and return an arbitrary set element.
        Raises KeyError if the set is empty.
        """
        pass

    def remove(self, *args, **kwargs): # real signature unknown
        """
        Remove an element from a set; it must be a member.
        
        If the element is not a member, raise a KeyError.
        """
        pass

    def symmetric_difference(self, *args, **kwargs): # real signature unknown
        """
        Return the symmetric difference of two sets as a new set.
        
        (i.e. all elements that are in exactly one of the sets.)
        """
        pass

    def symmetric_difference_update(self, *args, **kwargs): # real signature unknown
        """ Update a set with the symmetric difference of itself and another. """
        pass

    def union(self, *args, **kwargs): # real signature unknown
        """
        Return the union of sets as a new set.
        
        (i.e. all elements that are in either set.)
        """
        pass

    def update(self, *args, **kwargs): # real signature unknown
        """ Update a set with the union of itself and others. """
        pass