Basic text RLE compression (despite increasing file size in most cases)

rle.py

import sys

dotTxt = sys.argv[1]
textfile = open(dotTxt)
string = textfile.read()

compressed = []

noInRow = 1

for i in range(0, len(string)-1):
    prevLetter = string[i]
    nextLetter = string[i + 1]

    if nextLetter == prevLetter:
        noInRow += 1
    else:
        compressed.append([noInRow, prevLetter])
        noInRow = 1

compressed.append([noInRow, string[-1]])

finalStr = ""
for pair in compressed:
	finalStr += ''.join(str(x) for x in pair)
print(finalStr)

print("*" * 50)
print("INITIAL :", len(string))
print("FINAL   :", len(finalStr))