您可以使用merge，但首先区分左/右的列名（例如，使用add_suffix）：

out = df1.merge(df2.add_suffix('_'), how='outer',
                left_on=['level', 'title'],
                right_on=['level_', 'title_'])

字符串
输出量：

level          title   level_         title_
0  Level 0      Effective  Level 0      Effective
1  Level 1     Evaluation  Level 1     Evaluation
2  Level 1    Ice Breaker      NaN            NaN
3  Level 1           Fire      NaN            NaN
4  Level 2   Introduction  Level 2   Introduction
5  Level 2  Understanding  Level 2  Understanding
6  Level 3        Connect      NaN            NaN
7      NaN            NaN  Level 1         Comedy
8      NaN            NaN  Level 4        Connect

型
如果你想在合并的键上排序，另一种方法是：

out = (df1.merge(df2, how='outer',
                 left_on=[df1['level'], df1['title']],
                 right_on=['level', 'title'])
          .sort_values(by=['level'])
          #.drop(columns=['level', 'title']) # uncomment to drop merged keys
      )

型
输出量：

level          title  level_x        title_x  level_y        title_y
0  Level 0      Effective  Level 0      Effective  Level 0      Effective
1  Level 1     Evaluation  Level 1     Evaluation  Level 1     Evaluation
2  Level 1    Ice Breaker  Level 1    Ice Breaker      NaN            NaN
3  Level 1           Fire  Level 1           Fire      NaN            NaN
7  Level 1         Comedy      NaN            NaN  Level 1         Comedy
4  Level 2   Introduction  Level 2   Introduction  Level 2   Introduction
5  Level 2  Understanding  Level 2  Understanding  Level 2  Understanding
6  Level 3        Connect  Level 3        Connect      NaN            NaN
8  Level 4        Connect      NaN            NaN  Level 4        Connect

型