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

Question

I come from a sql background and I use the following data processing step frequently:

1. Partition the table of data by one or more fields
2. For each parti

Answer 1

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