Python数据类型之集合

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集合是高中数学中的一个概念,一堆确定的无序的唯一的数据,集合中每一个数据成为一个元素。

集合的特征:

  1. 集合内数据无序,即无法使用索引和分片;
  2. 集合内部数据元素具有唯一性,可以用来排除重复数据;
  3. 集合内的数据,str, int, float, tuple,冰冻集合等,即内部只能放置可哈希数据;
  4. 系测试,测试两组数据之前的交集、差集、并集、子集等关系。

集合的基本功能

集合创建:

>>> set_job = set(['DEV', 'OPS', 'DBA', 'QA', 'Sales'])
>>> set_man = set(('lucky', 'jack', 'andy', 'tom', 'andy', 'jim'))
>>> print(set_job, type(set_job))
{'DEV', 'OPS', 'Sales', 'QA', 'DBA'} <class 'set'>
>>> print(set_man, type(set_man))    # 天生去重,只有一个andy了
{'andy', 'jack', 'lucky', 'tom', 'jim'} <class 'set'>

元素添加:

>>> set_job = set(['DEV', 'OPS', 'DBA', 'QA', 'Sales'])
>>> set_job.add('HR')       # add方法只能添加一个
>>> print(set_job)
{'QA', 'HR', 'Sales', 'DEV', 'OPS', 'DBA'}

>>> set_job.update(['FD', 'MD', 'MD'])
>>> print(set_job)
{'QA', 'HR', 'Sales', 'DEV', 'MD', 'OPS', 'FD', 'DBA'}
>>> set_job.update(('AD', 'PD'))  # update方法可以添加是列表或者元组,去重,如果添加的为一个单独字符串,则把字符串拆成字母添加到集合中
>>> print(set_job)
{'QA', 'HR', 'PD', 'Sales', 'DEV', 'MD', 'OPS', 'AD', 'FD', 'DBA'}

元素删除:

>>> set_job = {'QA', 'HR', 'PD', 'Sales', 'DEV', 'MD', 'OPS', 'AD', 'FD', 'DBA'}
>>> set_job.remove('PD')   # 删除指定元素
>>> set_job.remove('xx')   # 元素不存在则报错 KeyError
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'xx'
>>> print(set_job)
{'QA', 'HR', 'MD', 'DEV', 'Sales', 'OPS', 'AD', 'FD', 'DBA'}
>>> set_job.pop()  # 随机删除一个元素
'QA'
>>> print(set_job)
{'HR', 'MD', 'DEV', 'Sales', 'OPS', 'AD', 'FD', 'DBA'}
>>> set_job.discard('OPS')  # 指定删除
>>> set_job.discard('xxx')  # 不存在返回None,不会报KeyError
>>> print(set_job)
{'HR', 'MD', 'DEV', 'Sales', 'AD', 'FD', 'DBA'}

其他:

>>> set_job = {'QA', 'HR', 'PD', 'Sales', 'DEV', 'MD', 'OPS', 'AD', 'FD', 'DBA'}
>>> len(set_job)  # 集合长度
10
>>> 'QA' in set_job  # 判断是否在集合中
True
>>> 'XXX' not in set_job # 不在集合中
True
>>> for i in set_job:   # 循环
...     print(i)

集合关系测试

交集:

>>> set_a = {5, 6, 7, 8, 9, 10}
>>> set_b = {1, 2, 3, 4, 5, 6}
>>> print(set_a.intersection(set_b))   # 常规方式
{5, 6}
>>> print(set_a & set_b)   # 运算符(&)方式
{5, 6}

并集:

>>> set_a = {5, 6, 7, 8, 9, 10}
>>> set_b = {1, 2, 3, 4, 5, 6}
>>> set_c = set_a.union(set_b)    # 关键字union做并集运算 先后顺序无关,谁并谁都可以
>>> print(set_c)
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
>>> 
>>> set_c = set_a | set_b     # 运算符关键符 | 做并集运算  先后顺序无关,谁并谁都可以
>>> print(set_c)
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

差集:

>>> set_a = {5, 6, 7, 8, 9, 10}
>>> set_b = {1, 2, 3, 4, 5, 6}
>>> set_c = set_a - set_b   # a集合跟b集合做差集 关键符 -
>>> print(set_c)
{8, 9, 10, 7}
>>> set_d = set_b - set_a   # b集合跟a集合做差集 关键符 -
>>> print(set_d)
{1, 2, 3, 4}
>>> set_c = set_a.difference(set_b) # a集合跟b集合做差集 关键字difference
>>> print(set_c)
{8, 9, 10, 7}
>>> set_d = set_b.difference(set_a) # b集合跟a集合做差集 关键字difference
>>> print(set_d)
{1, 2, 3, 4}

子集父集:

拿苹果来打比方就是,把苹果掰开,然后掰开的一小部分就是子集,然后整个苹果就是父集.

>>> set_a = {5, 6, 7, 8, 9, 10}
>>> set_b = {1, 2, 3, 4, 5, 6}
>>> set_c = {7, 8, 9, 10}
>>> set_d = {1, 2, 3, 4}
>>> set_e = {5, 6}
>>> set_f = {11, 12, 13, 14, 15, 16}
>>> set_c.issubset(set_a)   # 测试集合c是否是集合a的子集 放回布尔值  关键字issubset
True
>>> set_d.issubset(set_b)   # 测试集合d是否是集合b的子集 返回布尔值  issubset
True
>>> set_e.issubset(set_a)
True
>>> set_e.issubset(set_b)
True
>>> set_e <= set_a         # 测试集合e是否是集合a的子集 关键符 <=
True
>>> set_e <= set_b
True
>>> set_f.issuperset(set_a)  # 测试f集合是否是a集合的父集
False
>>> set_a.issuperset(set_e)  # 测试a集合是否是集合e的父集 关键字issuperset
True
>>> set_b >= set_e  # 测试集合b是否是集合e的父集 关键符 >=
True
>>> set_b >= set_d
True

对称差集:

对称差集就是两个集合去掉相同的部分,然后剩下的所有元素组成的集合

>>> set_a = {5, 6, 7, 8, 9, 10}
>>> set_b = {1, 2, 3, 4, 5, 6}
>>> set_c = set_a.symmetric_difference(set_b)  # 集合a和集合b做对称差集 关键字symmetric_difference 
>>> print(set_c)
{1, 2, 3, 4, 7, 8, 9, 10}
>>> set_c = set_a ^ set_b  # 集合a和集合b做对称差集 关键符 ^
>>> print(set_c)
{1, 2, 3, 4, 7, 8, 9, 10}
>>> set_c = set_b ^ set_a
>>> print(set_c)
{1, 2, 3, 4, 7, 8, 9, 10}

所有方法:

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
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