• Select or groupby one column in pandas datafram with multi-level index

To select one column in a datafram with multi-level index, you can use a tuple containing the names of the column in different levels to access desired column.

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df1 = df.groupby([('level0','level1')]).sum()

• the use of reset_index

Convert index level 0 to a column

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df.reset_index(level=0)

• Retrieve the index from multi-level index dataframe

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df.index.get_level_values(0)