Update index after sorting data-frame

Question

Take the following data-frame   x   np tile np arange 3  3  y   np repeat np arange 3  3  df   pd DataFrame   x   x   y   y        x  y 0  0  0 1  1  0 2  2  0 3  0  1 4  1  1 5  2  1 6  0  2 7  1  2 8  2  2   I need to sort it by x first  and only second by y   df2   df sort   x    y        x  y 0  0  0 3  0  1 6  0  2 1  1  0 4  1  1 7  1  2 2  2  0 5  2  1 8  2  2   How can I change the index such that it is ascending again  I e  how do I get this      x  y 0  0  0 1  0  1 2  0  2 3  1  0 4  1  1 5  1  2 6  2  0 7  2  1 8  2  2   I have tried the following  Unfortunately  it doesn t change the index at all   df2 reindex np arange len df2 index

User · Answer

You can set new indices by using set index      df2 set index np arange len df2 index      Output      x  y 0  0  0 1  0  1 2  0  2 3  1  0 4  1  1 5  1  2 6  2  0 7  2  1 8  2  2

User · Answer

You can reset the index using reset index to get back a default index of 0  1  2       n-1  and use drop True to indicate you want to drop the existing index instead of adding it as an additional column to your dataframe    In  19   df2   df2 reset index drop True   In  20   df2 Out 20      x  y 0  0  0 1  0  1 2  0  2 3  1  0 4  1  1 5  1  2 6  2  0 7  2  1 8  2  2

User · Answer

Since pandas 1 0 0 df sort values has a new parameter ignore index which does exactly what you need   In  1   df2   df sort values by   x   y   ignore index True   In  2   df2 Out 2      x  y 0  0  0 1  0  1 2  0  2 3  1  0 4  1  1 5  1  2 6  2  0 7  2  1 8  2  2

User · Answer

df sort   is deprecated  use df sort values       https   pandas pydata org pandas-docs stable generated pandas DataFrame sort values html  Then follow joris  answer by doing df reset index drop True

[python] Update index after sorting data-frame

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