CODEWITHSUNDEEP
pythonfilefor-loopinput
Joe
Joe

Reputation: 83

Python For Loop with File

I'm still learning Python and decided to combine two different elements to understand loops and files better. I made a simple for loop that takes multiple inputs from the user and writes it into a file. I read and watch some tutorials on how to work with for loop and files. What I wanted to do is every time the user writes a line of string a number will be written at the beginning stating the position.

So, if I only write one line then the for loop will also write the number "1" at the beginning. If I write two lines of strings then it will be

  1. string
  2. string

The problem I'm having with this is that this method only works if I keep writing different lines of string in that debugging only.

If I stop writing and decide to start the loop again to write a new line then it start with number "1" again. Any idea how can I fix this and why is it happening?

Upvotes: 0

Views: 417

Answers (2)

Osadhi Virochana
Osadhi Virochana

Reputation: 1302

Your code has several problems. So I recreated your code.

try:
    with open("file.txt", "r") as l:
        line = int(l.readlines()[-1][0]) + 1
except FileNotFoundError:
    line = 1

This tries to read the file and get the last number if it doesn't exist it use 1.

with open("file.txt", "a") as f:
    try:
        while True: 
            f.write(f'{line} {input()} \n')
            line += 1
    except KeyboardInterrupt:
        print('Quiting...')

This is same as your code but I add a way to exit(ctrl+c) without giving an error message.

So the final code will be like this:

try:
    with open("file.txt", "r") as l:
        line = int(l.readlines()[-1][0]) + 1
except FileNotFoundError:
    line = 1

with open("file.txt", "a") as f:
    try:
        while True: 
            f.write(f'{line} {input()} \n')
            line += 1
    except KeyboardInterrupt:
        print('Quiting...')

Upvotes: 1

henos
henos

Reputation: 70

The way to do that would be to read the file, then find the most recent line, and get that number.

You would then add 1 to it, and keep going from there

P.S. regex will help

Upvotes: 1

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