def delete_last_line():
    with open('test.txt', "r+", encoding="utf-8") as file:

        # Move the pointer (similar to a cursor in a text editor) to the end of the file
        file.seek(0, os.SEEK_END)

        # This code means the following code skips the very last character in the file -
        # i.e. in the case the last line is null we delete the last line
        # and the penultimate one
        pos = file.tell() - 1

        # Read each character in the file one at a time from the penultimate
        # character going backwards, searching for a newline character
        # If we find a new line, exit the search
        while pos > 0 and file.read(1) != "\n":
            pos -= 1
            file.seek(pos, os.SEEK_SET)

        # save value of last line
        value = file.readline()

        # So long as we're not at the start of the file, delete all the characters ahead
        # of this position
        if pos > 0:
            file.seek(pos, os.SEEK_SET)
            file.truncate()

        return value