[FIXED] Python script to delete lines with repetitive strings

Issue

This
This line 
This line has
This line has five
This line has five strings

I need the script to delete lines 1 through 4 and just print line 5

This looks for exact lines so did not work for me:

lines_seen = set() # holds lines already seen
outfile = open(outfilename, "w")
for line in open(infilename, "r"):
    if line not in lines_seen: # not a duplicate
        outfile.write(line)
        lines_seen.add(line)
outfile.close()

Solution

with open(infilename) as fin:
    lines = list(map(str.rstrip, fin))
i = 0
while i < len(lines):
    while i + 1 < len(lines) and lines[i + 1].startswith(lines[i]):
        i += 1  # duplicate, so skip
    print(lines[i])
    i += 1

Feel free to send those surviving lines to an output file, if desired.

Answered By - J_H