Re Ranking data within a csv after row removal

Question 1

Store a set of itertools.count() iterables in a dictionary, to keep a counter per unique column value. If you use collections.defaultdict(), you can have the count start at 1 automatically whenever you encounter a new unique value.

Your data is already sorted, so all you need to do is replace the 10th column:

import csv
from itertools import count
from collections import defaultdict
from functools import partial

counts = defaultdict(partial(count, 1))  # create a new count starting at 1

with open(output_csv_filename, 'wb') as outfile:
    writer = csv.writer(outfile)
    for row in your_list_of_rows:
        row[9] = next(counts[row[2]])  # get the next count value
        writer.writerow(row)

That's it. row[9] is the 10th column; it'll be filled with numbers starting at 1 for each unique value found in row[2] (the 3rd column).

Quick demo of the counters dictionary:

>>> from itertools import count
>>> from collections import defaultdict
>>> from functools import partial
>>> counts = defaultdict(partial(count, 1))
>>> next(counts['foo'])
1
>>> next(counts['foo'])
2
>>> next(counts['bar'])
1
>>> next(counts['foo'])
3

Running the above code on your sample data set results in:

1-20,data1,Unique data1,4,data2,14,data3.65,data4,data5,1,141.85,data data data
1-20,data1,Unique data1,4,data2,14,data3.65,data4,data5,2,140.81,data data data
1-20,data1,Unique data1,4,data2,14,data3.65,data4,data5,3,131.86,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,1,163.85,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,2,162.93,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,3,161.23,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,4,159.83,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,5,156.71,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,6,154.96,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,7,147.96,data data data
1-30,data1,Unique data2,4,data2,12,data3.30,data4,data5,8,140.09,data data data
1-50,data1,Unique data3,2,data2,16,data3.00,data4,data5,1,169.5,data data data
1-50,data1,Unique data3,2,data2,16,data3.00,data4,data5,2,165.2,data data data
1-50,data1,Unique data3,2,data2,16,data3.00,data4,data5,3,165.1,data data data
1-50,data1,Unique data3,2,data2,16,data3.00,data4,data5,4,159.8,data data data

Question 2

So, you want to rank your rows by 3rd then by 10th element, right?

Read file

ext = "C:\Users\Me\Desktop\\test.txt"
readL = []

f = open(ext)

for line in f:

    readL += [line.strip().split(',')]   

f.close()

sort list of lines by elements 3 then 10:

from operator import itemgetter
print sorted(readL, key=itemgetter(3,10))