在Python中找到两个字典列表之间的区别 [英] Finding difference between two list of dictionary in Python

问题描述

我正在尝试查找2个字典列表之间的区别.我在这个论坛上找到了一些信息，但没有达到我的目的.

I am trying to find the difference between 2 list of dictionary. I found some information in this forum but did not serve my purpose.

incoming_rows = [{'column_name': 'LOAD_ID', 'data_type': 'int', 'table_name': 'CONFIG'},
            {'column_name': 'ROW_NUMBER', 'data_type': 'int', 'table_name': 'CONFIG'},
            {'column_name': 'CREATE_DATE', 'data_type': 'VARCHAR(20)', 'table_name': 'CONFIG'},
            {'column_name': 'CONFIG_TYPE', 'data_type': 'varchar(1)', 'table_name': 'CONFIG'},
            {'column_name': 'CONFIG_ID', 'data_type': 'numeric(10,0)', 'table_name': 'CONFIG'}
            ]

available_row = [{'column_name': 'LOAD_ID', 'data_type': 'int', 'table_name': 'CONFIG'},
             {'column_name': 'ROW_NUMBER', 'data_type': 'int', 'table_name': 'CONFIG'},
             {'column_name': 'CREATE_DATE', 'data_type': 'date', 'table_name': 'CONFIG'}
             ]

在这里我需要将传入行与字典的available_row列表进行比较，而差异要以另一种dict格式列表进行列出.在这里，我的表名是唯一的. 情况: 1.任何新添加的列. 2.数据类型的任何更改 如果这两个条件都成立，则Expected_row应该只包含这些更改的行.

Here I need to compare the incoming_rows with the available_row list of dictionary and the difference want to list in another list of dict format.Here my table name is unique. Conditions: 1. Any new addition of columns. 2. Any change in data type If these two conditions are true then the the expected_row should contain only these changed rows only.

# expected output
expected_row=[{'column_name': 'CONFIG_TYPE', 'data_type': 'varchar(1)', 'table_name': 'CONFIG'},
          {'column_name': 'CONFIG_ID', 'data_type': 'numeric(10,0)', 'table_name': 'CONFIG'},
          {'column_name': 'CREATE_DATE', 'data_type': 'VARCHAR(20)', 'table_name': 'CONFIG'}
        ]

推荐答案

集合是解决此问题的理想解决方案.不幸的是，python不允许您将字典添加到集合中，因为它们是可变的，并且其哈希码可能会在插入和查找之间改变.

A set is the perfect solution for this problem. Unfortunately, python will not let you add dictionaries to a set, because they are mutable and their hashcode could change between insert and lookup.

如果冻结"项目以使其不可变，则可以将其添加到设置对象而不是列表中；然后使用减号运算符设置一个差异:

If you "freeze" the items to make them immutable, you can then add them to set objects instead of a list; and then take a set difference using the minus operator:

In [20]: i_set = { frozenset(row.items()) for row in incoming_rows }

In [21]: a_set = { frozenset(row.items())  for row in available_row }

In [22]: (i_set - a_set)
Out[22]: 
{frozenset({('column_name', 'CONFIG_ID'),
            ('data_type', 'numeric(10,0)'),
            ('table_name', 'CONFIG')}),
 frozenset({('column_name', 'CREATE_DATE'),
            ('data_type', 'VARCHAR(20)'),
            ('table_name', 'CONFIG')}),
 frozenset({('column_name', 'CONFIG_TYPE'),
            ('data_type', 'varchar(1)'),
            ('table_name', 'CONFIG')})}

要取消冻结:

In [25]: [dict(i) for i in i_set - a_set]
Out[25]: 
[{'column_name': 'CONFIG_ID',
  'data_type': 'numeric(10,0)',
  'table_name': 'CONFIG'},
 {'column_name': 'CREATE_DATE',
  'data_type': 'VARCHAR(20)',
  'table_name': 'CONFIG'},
 {'column_name': 'CONFIG_TYPE',
  'data_type': 'varchar(1)',
  'table_name': 'CONFIG'}]

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