如果两列中的值不同，则在数据帧中创建新行

Question

假设我有一个像这样的数据帧：

Col1   Col2   Tag_history   New_tag      Col5           created
0  Name1    Value1    Tag10      Tag10       Rank4     2021-03-21 12:58:09
1  Name1    Value2    Tag10      Tag10       Rank4     2021-03-21 13:58:09
2  Name1    Value3    Tag10      Tag10       Rank4     2021-03-21 14:58:09
3  Name2    Value1    Tag8       Tag9        Rank1     2021-03-21 10:58:09
4  Name2    Value2    Tag8       Tag9        Rank1     2021-03-21 11:58:09
5  Name2    Value4    Tag8       Tag9        Rank1     2021-03-21 12:58:09
6  Name2    Value5    Tag8       Tag9        Rank1     2021-03-21 13:58:09

因此，我想比较列Tag_history和New标记，如果标记已经更改，我想添加一个新行，在Tag_histry中也显示新的标记。例如，对于Name2，标签已经从Tag8更改为Tag9，所以我希望我的df看起来像这样：

Col1   Col2   Tag_history   New_tag       Col5          created
0  Name1    Value1    Tag10      Tag10       Rank4    2021-03-21 12:58:09
1  Name1    Value2    Tag10      Tag10       Rank4    2021-03-21 13:58:09
2  Name1    Value3    Tag10      Tag10       Rank4    2021-03-21 14:58:09
3  Name2    Value1    Tag8       Tag9        Rank1    2021-03-21 10:58:09
4  Name2    Value2    Tag8       Tag9        Rank1    2021-03-21 11:58:09
5  Name2    Value4    Tag8       Tag9        Rank1    2021-03-21 12:58:09
6  Name2    Value5    Tag8       Tag9        Rank1    2021-03-21 13:58:09
7  Name2    IDLE      Tag9       Tag9        Rank1    2022-01-24 16:50:00 (current datetime)

Answer 1

首先，我不建议使用任何循环，因为它们不是很有效。

different_value = df[~(df['Tag_history'] == df['New_tag'])] #First check and search for rows that contains different "Tag_history" and "New_tag"
different_value.loc[:,'New_tag'] = different_value['Tag_history']  #Create the new rows
df = df.append(different_value, ignore_index = True) # append dataframes