Comprehension List and new File

Question

Example of two text files. The left image is before, the right one is after

I need to swap the dates in one file and put it on a new file using comprehension lists. How would I do that? This is what I have:

list1 = [x.replace("\n","").replace("/"," ").split(" ") for x in open("dobA.txt")]
list2 = [(i[len(i)-2],i[len(i)-3]) for i in list1]
with open("dobB.txt", "w") as newfile:
        newfile.write()

The top line of code makes the dates into their own string, such as "10".

The second line of code swaps the numbers I need but only prints out: [('11', '10'), ('8', '9'), ('9', '7')]

The last two are just writing a new file.

How would I swap these two numbers and put them on a new file? Thank you.

Answer 1

First of all, do this:

i[-2]

instead of

i[len(i)-2]

There are a couple of options to approach this:

Readable one without comprehensions:

with open("old_file.txt") as old_file, open("new_file.txt", "w") as new_file:
    for line in old_file:
        name, surname, date = line.split()
        day, month, year = date.split("/")
        print(f"{name} {surname} {month}/{day}/{year}", file=new_file)

Regex replace:

import re
from pathlib import Path

text = Path("old_file.txt").read_text()
replaced = re.sub(r"(\d+)/(\d+)/(\d+)", r"\2/\1/\3", text)
Path("new_file.txt").write_text(replaced)

If you really need comprehensions:

with open("old_file.txt") as old_file, open("new_file.txt", "w") as new_file:
    new_lines = [
        f"{text} {date.split('/')[1]}/{date.split('/')[0]}/{date.split('/')[2]}"
        for text, date in [line.rsplit(maxsplit=1) for line in old_file]
    ]
    print("\n".join(new_lines), file=new_file)