pandas 索引与列相互转化

<code>df.set_index('date')</code>

<code>df['index'] = df.index</code>

<code>df.reset_index(level=0, inplace=True)</code>

<code>df.reset_index(level=['tick', 'obs'])</code>

<code>df['si_name'] = df.index.get_level_values('si_name')</code> # where si_name is the name of the subindex.