Python program to delete a specific line in a text file [duplicate]

Answer 1

You know that line6 == lines[5], so the condition if lines[5] != line6: is never true and thus you never write anything to the file

Answer 2

You should check your logic and variable names. You're checking if lines[5] is not equal to line6, everytime in your loop. Which it is, because it IS that exact line. You want the check the current line:

if t == "dy":
    f = open("C:/Users/Sreeraj/Desktop/Thailand_Rectangle2_National Parks.txt","w")
    for line in lines:
        if line != line6: # <- Check actual line!
            f.write(line)

f.close()

Answer 3

Your problem is that lines[5] will always be equal to line6. You never modified the sixth line in lines, so line6 and lines[5] are still equal. Thus, the condition lines[5] != line6 will always fail.

If you want to always remove the sixth line from your file, you can use enumerate. For example:

with open("file.txt", "r") as infile:
    lines = infile.readlines()

with open("file.txt", "w") as outfile:
    for pos, line in enumerate(lines):
        if pos != 5:
            outfile.write(line)

Answer 4

The actual error in your way to do this was already pointed out, but instead of comparing the content of each line, I recommend you simply compare the line number or use startswith. Otherwise you are doing a lot of unneeded string comparisons, which can be costly.

Other improvements could be to handle your file using with, opening the file only once and allowing to delete multiple lines at once.

# 'r+' allows you to read and write to a file
with open("test.txt", "r+") as f:
    # First read the file line by line
    lines = f.readlines()

    # Go back at the start of the file
    f.seek(0)

    # Filter out and rewrite lines
    for line in lines:
        if not line.startswith('dy'):
            f.write(line)

    # Truncate the remaining of the file
    f.truncate()