Python集合及其运算

（一）集合 set

集合是由不同可hash的值组成的，里面所有的值都是唯一的,也是无序的

集合的创建

>>>set_test = {"name", "age", "hometown"}
##  把值放入{ }中

>>>lis = ("name", "age", "hometown")
>>>set_test = set(lis)
>>> set_test
{'name', 'age', 'hometown'}
##利用set（）函数，把其他类型转换为set

>>> list_test = ["name", "age", "hometown"]
>>> set_test = frozenset(list_test)
>>> set_test
frozenset({'name', 'age', 'hometown'})
##利用frozenset()函数可以创造一个set，并把它放到元组里面

---

集合的操作

• add(self, *args, **kwargs)

  添加值到集合里面

  >>> set_test
  {'name', 'age', 'hometown'}
  >>> set_test.add("hobby")
  >>> set_test
  {'name', 'age', 'hobby', 'hometown'}

• clear(self, *args, **kwargs)

  清空集合

• copy(self, *args, **kwargs)

  浅拷贝

• discard(self, *args, **kwargs)

  删除某值，没有时不会报错

  >>> set_test
  {'name', 'age', 'hobby', 'hometown'}
  >>> set_test.discard("hobby")
  >>> set_test
  {'name', 'age', 'hometown'}

• pop(self, *args, **kwargs)

  当集合是由列表和元组组成时,set.pop()是从左边删除元素的，并且可以得到被删除的值

  >>> set_test
  {'name', 'age', 'hometown'}
  >>> set_test.pop()
  'name'
  >>> set_test.pop()
  'age'

• remove(self, *args, **kwargs)

  删除某值，但是如果没有的话，就会报错

  >>> set_test = {'name', 'age', 'hometown'}
  >>> set_test.remove("hometown")
  >>> set_test
  {'name', 'age'}

• update(self, *args, **kwargs)

  更新值，可以在set里面添加多个值

  >>> set_test = {"Jack", "Mark", "Ada"}
  >>> set_test.update(["Jewish", "Obanma", "Anna"])
  >>> print(set_test)
  {'Obanma', 'Mark', 'Jack', 'Anna', 'Ada', 'Jewish'}

集合的运算

• 求交集

  >>> set_test1 = {"YuanMing", "Hermaeus", "Chenglong", "Kelan"}
  >>> set_test2 = {"YuanMing", "Hermaeus", "ZhangJie","Jack"}
  
  >>> test_result = set_test1.intersection(set_test2)
  >>> print(test_result)
  {'YuanMing', 'Hermaeus'}
  
  >>> test_result = set_test1&set_test2
  >>> print(test_result)
  {'YuanMing', 'Hermaeus'}

• 求并集

  >>> set_test1 = {"YuanMing", "Hermaeus", "Chenglong", "Kelan"}
  >>> set_test2 = {"YuanMing", "Hermaeus", "ZhangJie","Jack"}
  
  >>> test_result = set_test1.union(set_test2)
  >>> print(test_result)
  {'Kelan', 'YuanMing', 'ZhangJie', 'Jack', 'Hermaeus', 'Chenglong'}
  
  >>> test_result = set_test1|set_test2
  >>> print(test_result)
  {'Kelan', 'YuanMing', 'ZhangJie', 'Jack', 'Hermaeus', 'Chenglong'}

• 求差集

  >>> set_test1 = {"YuanMing", "Hermaeus", "Chenglong", "Kelan"}
  >>> set_test2 = {"YuanMing", "Hermaeus", "ZhangJie","Jack"}
  
  >>> test_result = set_test1.difference(set_test2)
  >>> test_result1 = set_test1.difference(set_test2)
  >>> print(test_result1)
  {'Kelan', 'Chenglong'}
  
  >>> test_result1 = set_test1-set_test2
  >>> print(test_result1)
  {'Kelan', 'Chenglong'}
  
  >>> test_result2 = set_test2.difference(set_test1)
  >>> print(test_result2)
  {'ZhangJie', 'Jack'}
  
  >>> test_result2 = set_test2-set_test1
  >>> print(test_result2)
  {'ZhangJie', 'Jack'}

• 求交叉补集

  >>> set_test1 = {"YuanMing", "Hermaeus", "Chenglong", "Kelan"}
  >>> set_test2 = {"YuanMing", "Hermaeus", "ZhangJie","Jack"}
  >>> test_result = set_test1.symmetric_difference(set_test2)
  >>> print(test_result)
  {'ZhangJie', 'Jack', 'Kelan', 'Chenglong'}
  >>> test_result = set_test1^set_test2
  >>> print(test_result)
  {'ZhangJie', 'Jack', 'Kelan', 'Chenglong'}

• 求集赋值

  • symmetric_difference_update(self, *args, **kwargs)

    >>> set_test1 = {"Jack", "Mark", "Devid"}
    >>> set_test2 = {"Jack", "Marish", "Good"}
    
    >>> set_test1.symmetric_update(set_test2)
    >>> set_test1.symmetric_difference_update(set_test2)  ## 把得到值赋予set_test1
    >>> set_test1, set_test2
    ({'Good', 'Marish', 'Devid', 'Mark'}, {'Good', 'Jack', 'Marish'})
    
    >>> set_test1 ^= set_test2           
    >>> set_test1            
    {'Good', 'Marish', 'Devid', 'Mark'}

  • intersection_update(self, *args, **kwargs)

    >>> set_test1 = {"Jack", "Mark", "Devid"}
    >>> set_test2 = {"Jack", "Marish", "Good"}
    
    >>> set_test1.intersection_update(set_test2)  ##把得到的值赋予set_test1
    >>> set_test1, set_test2
    ({'Jack'}, {'Good', 'Jack', 'Marish'})
    
    >>> set_test1 &= set_test2           
    >>> set_test1            
    {'Jack'}

  • difference_update(self, *args, **kwargs)

    >>> set_test1 = {"Jack", "Mark", "Devid"}
    >>> set_test2 = {"Jack", "Marish", "Good"}
    
    >>> set_test1.difference_update(set_test2)
    >>> set_test1, set_test2
    ({'Devid', 'Mark'}, {'Good', 'Jack', 'Marish'})
    >>> set_test1 = {"Jack", "Mark", "Devid"}            
    >>> set_test2 = {"Jack", "Marish", "Good"}  
    
    >>> set_test1 -= set_test2           
    >>> set_test1            
    {'Devid', 'Mark'}

  • set_test1 |= set_test2

    >>> set_test1 = {"Jack", "Mark", "Devid"}           
    >>> set_test2 = {"Jack", "Marish", "Good"}
    >>> set_test1 |= set_test2          
    >>> set_test1      

---

子集与父集

• issubset(self, *args, **kwargs)

  A.issubset(B) A是B的子集吗？ 返回bool

  >>> set_test2 = {"Jack", "Marish", "Good"}
  >>> set_test1 = {"Jack"}
  >>> set_test2.issubset(set_test1)
  False
  >>> set_test1.issubset(set_test2)
  True

• issuperset(self, *args, **kwargs)

  A.issuperset(B) A是B的父集吗？ 返回bool

  >>> set_test2 = {"Jack", "Marish", "Good"}
  >>> set_test1 = {"Jack"}
  >>> set_test1.issuperset(set_test2)
  False
  >>> set_test2.issuperset(set_test1）            
  True

• isdisjoint(self, *args, **kwargs)

  返回True如果两个set没有交集

  >>> set_test1 = {"Jack", "Mark", "Devid"}      
  >>> set_test2 = {"Ada", "Marish", "Good"}          
  >>> set_test1.isdisjoint(set_test2)            
  True

• <，<= OR >，>=

  >>> set_test1 = {"Jack", "Mark", "Devid"}          
  >>> set_test2 = {"Jack", "Mark"
  >>> set_test1 < set_test2          
  False
  >>> set_test1 > set_test2          
  True