字符串切片不接受变量

Question

I am writing a short method to slice a string based upon the index of comma's in a different method. I droped everything into one code for easy viewing.

with open(testconfig) as f:
        lines=f.readlines()
        initlist=[]
        string_slice_list=[]
        b=0
        for line in lines:
            if "ML_STARConfig" in line:
                b+=1
                liste=sfind(line,",")
                liste.insert(0,0)
                input("line is {}sfind list of characters is {} and there should be a zero in position 0".format(line,liste))
                liste=list(reversed(liste))
                slices=[]
                for i in range(1,len(liste)):#make a list of tuples that have the beginning and end indexes of a "useful slice" of the string "line"
                    slices.append((liste[i-1],liste[i]))
                for item in slices:
                    b=item[0]
                    e=item[1]
                    word=line[b:e]
                    input("line is {} word indexes are {},{} and this should be a word ={}".format(line,b,e,word))

the method accepts a single line from a file and creates a list of the indexes of the comma's in the line. I assign each pair of indexes to a tuple and append each tuple to a list. and then loop over the list of tuples to extract each of the words of interest from the line. Except when I pass the numbers from the list of tuples it will not slice the string. and returns nothing in the last line. Here is my stack trace or this code...

line is ML_STARConfig, Master, C0RF, , rf, 7.1S B 2011-10-05, Firmware version
sfind list of characters is [0, 13, 21, 27, 29, 33, 52] and there should be a zero in position 0
line is ML_STARConfig, Master, C0RF, , rf, 7.1S B 2011-10-05, Firmware version
  word indexes are 52,33 and this should be a word =
line is ML_STARConfig, Master, C0RF, , rf, 7.1S B 2011-10-05, Firmware version
  word indexes are 33,29 and this should be a word =
line is ML_STARConfig, Master, C0RF, , rf, 7.1S B 2011-10-05, Firmware version
  word indexes are 29,27 and this should be a word =
line is ML_STARConfig, Master, C0RF, , rf, 7.1S B 2011-10-05, Firmware version
  word indexes are 27,21 and this should be a word =
line is ML_STARConfig, Master, C0RF, , rf, 7.1S B 2011-10-05, Firmware version
  word indexes are 21,13 and this should be a word =
line is ML_STARConfig, Master, C0RF, , rf, 7.1S B 2011-10-05, Firmware version
  word indexes are 13,0 and this should be a word =

the Variable for the line clearly works and the variable for the beginning and end indexes are there but the line[#:#] command just magically stops working and its very frustrating. I have no Idea what is causing this. I have tried making a list of lists of comma indexes and it is still not working.

What on earth am I missing here?

Answer 1

I reversed the order of the slice and that fixed it. Sorry I didnt realize I was trying to perform the slice in reverse, apparently this doesnt work.

to clarify, if you do

line[b:e]

and b>e it will give you a whole lot of nothing.