use of the while loop in this condition

Question

I got data that looks like this(below), I would like to write a while loop using python that goes line by line, and as long as the word in the first column is not changing the scripts check the value of the third column and if the value of the third column is the minimum it gives back the value of the third column and the value of the second column of the same line.

ZYG11B  0000  1
ZYG11B 0100 2
ZYG11B  0001 3
ZYG11A 0001000000000000 1
ZYG11A  0011000000000000 2
ZYG11A  0000000000000000 3
ZYG11A  0011000001000000 4
ZYG11A  0001000100000000 5
ZYG11A  0011000001000100 6
ZYG11A  0001000001000000 7
ZYG11A  0001000001000100 8
ZYG11A 0000000100000000 9
ZYG11A  0011010000000000 10
ZYG11A  0001010000000000 11
ZYG11A  0011000000010000 12
ZYG11A  0000000000000001 13
ZYG11A  0001000000000001 14
ZYG11A  0000010000000000 15
ZYG11A  0001000000010000 16
ZYG11A  0000110000000000 17
ZYG11A  0101000000000000 18
ZYG11A  0100000000000000 19
ZYG11A  0011010001000000 20
ZYG11A  0011000011000000 21
ZYG11A  0011110000000000 22
ZYG11A  0011010001000100 23
ZYG11A  0011000011001100 24
ZYG11A  0011000011000100 25
ZYG11A  0001000101000100 26
ZYG11A  0001000000000100 27
ZYG11A  0000110000000001 28
ZYG11A  0000001100000000 29

Answer 1

1. You can easily write your third column value to variable A and on each iteration write new value to new variable B and compare them.
2. Are these columns written in csv, list or it's just string?

Answer 2

If the Python 2.7 code below doesn't solve your problem, it should at least give you a starting point:

def ret_fields(file1):
    prev_category = ''
    min_field = 0
    ret_list = []
    line = file1.readline()
    while (line):
        [category,zero_one,field] = line.split()
        if (prev_category == ''):
            prev_category = category
            min_field = field

        if (category != prev_category):
            min_field = field

        if (int(field) <= int(min_field)):
            ret_list.append([category,zero_one,field])
            min_field = field
        
        prev_category = category
        line = file1.readline()
    
    return ret_list


f = open("fields.txt")
try:
    l = ret_fields(f)
    for i in l:
       print i

finally:
    f.close()

With the "fields.txt" file as follows:

ZYG11B  0000  1
ZYG11B 0100 2
ZYG11B  0001 3
ZYG11B  1000  0
ZYG11A 0001000000000000 1
ZYG11A  0011000000000000 2
ZYG11A  0000000000000000 3
ZYG11A  0011000001000000 4
ZYG11A  0001000100000000 5
ZYG11A  0011000001000100 6
ZYG11A  0001000001000000 7
ZYG11A  0001000001000100 8
ZYG11A 0000000100000000 9
ZYG11A  0011010000000000 10
ZYG11A  0001010000000000 11
ZYG11A  0011000000010000 12
ZYG11A  0000000000000001 13
ZYG11A  0001000000000001 14
ZYG11A  0000010000000000 15
ZYG11A  0001000000010000 16
ZYG11A  0000110000000000 17
ZYG11A  0000110000000000 -1
ZYG11A  0101000000000000 18
ZYG11A  0100000000000000 19
ZYG11A  0011010001000000 20
ZYG11A  0011000011000000 21
ZYG11A  0011110000000000 22
ZYG11A  0011010001000100 23
ZYG11A  0011000011001100 24
ZYG11A  0011000011000100 25
ZYG11A  0001000101000100 26
ZYG11A  0001000000000100 27
ZYG11A  0000110000000001 28
ZYG11A  0000001100000000 29
ZYG11A 1001000000000000 0

The output is:

$ python min_fields.py 
['ZYG11B', '0000', '1']
['ZYG11B', '1000', '0']
['ZYG11A', '0001000000000000', '1']
['ZYG11A', '0000110000000000', '-1']
$