I have a text file that looks like this:

```
1,004,59
1,004,65
1,004,69
1,005,55
1,005,57
1,006,53
1,006,59
1,007,65
1,007,69
1,007,55
1,007,57
1,008,53

```

Want to create new text file that will be inserted by 'input', something like this

```
1,004,59,input
1,004,65,input
1,004,69,input
1,005,55,input
1,005,57,input
1,006,53,input
1,006,59,input
1,007,65,input
1,007,69,input
1,007,55,input
1,007,57,input
1,008,53,input

```

I have attempted something like this:

```
with open('data.txt', 'a') as f:
    lines = f.readlines()
    for i, line in enumerate(lines):
            line[i] = line[i].strip() + 'input'
    for line in lines:
        f.writelines(line)

```

Not able to get the right approach though.