I have a data frame with two columns :

state  total_sales
AL      16714
AR      6498
AZ      107296
CA      33717

Now I want to map the strings in state column to int from 1 to N(where N is the no of rows,here 4 ) based on increasing order of values in total_sales . Result should be stored in another column (say label). That is, wanted a result like this :

state  total_sales label
AL      16714         3
AR      6498          4
AZ      107296        1
CA      33717         2

Please suggest a vectorised implementation .

You can use rank with cast to int:

df['label'] = df['total_sales'].rank(method='dense', ascending=False).astype(int)
print (df)
  state  total_sales  label
0    AL        16714      3
1    AR         6498      4
2    AZ       107296      1
3    CA        33717      2