SQL-like window functions in PANDAS: Row Numbering in Python Pandas Dataframe

by

you can also use sort_values(), groupby() and finally cumcount() + 1:

df['RN'] = df.sort_values(['data1','data2'], ascending=[True,False]) \
             .groupby(['key1']) \
             .cumcount() + 1
print(df)

yields:

   data1  data2 key1  RN
0      1      1    a   1
1      2     10    a   2
2      2      2    a   3
3      3      3    b   1
4      3     30    a   4

PS tested with pandas 0.18

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