一文看懂Python中的集合运算&，|，-，^

本是古典何须时尚 2023-03-14 13:59 11749阅读 0赞

## 关于集合的概念 ##

Python 中常用的集合方法是执行标准的数学运算，例如：求并集、交集、差集以及对称差。下图显示了一些在集合 A 和集合 B 上进行的标准数学运算。每个韦恩（Venn）图中的红色部分是给定集合运算得到的结果。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1ODY2NzM2_size_16_color_FFFFFF_t_70]

## Python中相应符号： ##

*  `&`符号在Python中既可以执行通常的按位与运算，也可以执行`set`集合里面的交集运算
 *  `|`：并集；也可以表示数字运算中的按位或运算
 *  `-`：差集
 *  `^`：对称差集

## 举例 ##

pre = ["berry","grape","pea_r","apple","banana","pear"]
    pos = ["apple","banana","pear","potato","cucumber"]
    pre_set = set(pre)  # 转换list为集合set
    pos_set = set(pos)
    
    union = pos_set | pre_set  # 并集
    print('The union of the two sets above is:\n{}\n'.format(union))
    
    intersection = pos_set & pre_set  # 交集
    print('The intersection of two sets is:\n{}\n'.format(intersection))
    
    only_in_preset = pre_set - pos_set  # 差集
    print('The unique part in pre_set is:\n{}\n'.format(only_in_preset))
    
    only_in_posset = pos_set - pre_set  # 差集
    print('The unique part in pos_set is:\n{}\n'.format(only_in_posset))
    
    sym_set_diff = pos_set^pre_set      # 对称差集
    print('The symmetric set difference of the two sets is:\n{}'.format(sym_set_diff))

输出结果如下：

The union of the two sets above is:
    {'potato', 'grape', 'banana', 'pear', 'berry', 'pea_r', 'cucumber', 'apple'}
    
    The intersection of two sets is:
    {'pear', 'apple', 'banana'}
    
    The unique part in pre_set is:
    {'berry', 'grape', 'pea_r'}
    
    The unique part in pos_set is:
    {'potato', 'cucumber'}
    
    The symmetric set difference of the two sets is:
    {'potato', 'pea_r', 'berry', 'cucumber', 'grape'}

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