Append Float Data At The End Of Each Line In A Text File

I have a .txt file and I'm trying to add float number at the end of each line with incremented value than the last line. This is what I have in the .txt file: >520.980000 172.90

Solution 1:

I would do it following way: Assume that you have file input.txt:

520.980000 172.900000 357.440000
320.980000 192.900000 357.441000
325.980000 172.900000 87.440000

then:

from decimal import Decimal
import re
counter = Decimal('1.0')

def get_number(_):
    global counter
    counter += Decimal('0.1')
    return " "+str(counter)+'\n'

with open("input.txt","r") as f:
    data = f.read()

out = re.sub('\n',get_number,data)

with open("output.txt","w") as f:
    f.write(out)

After that output.txt is:

520.980000 172.900000 357.440000 1.1
320.980000 192.900000 357.441000 1.2
325.980000 172.900000 87.440000 1.3

Note that I used Decimal to prevent problems with float (like something.999999...) appearing. I used regular expression (re) to find newlines (\n) and replace it with subsequent numbers by passing function as 2nd re.sub argument.

Solution 2:

Without other modules (not that you should avoid them!):

with open("numbers.txt", "rt") as fin:
    with open("numbers_out.txt", "wt") as fout:
        counter = 1.0
        for line in fin:
            counter += 0.1
            fout.write(f"{line.rstrip()} {counter:.1f}\n")

numbers_out.txt:

>520.980000 172.900000 357.440000 1.1
>320.980000 192.900000 357.441000 1.2
>325.980000 172.900000 87.440000 1.3