Line Terminator Class

funkylines.py

#! /usr/bin/env python3

"""
Silly implementation of a class which can emulate open()
while passing in a special lineterminator.

Not tested at all.

Author: Adam Silkey
Ref: https://discuss.python.org/t/41511
"""

import re

class FunkyLines:
    def __init__(self, s: str, lineterminator: str):
        self.s = s
        self.lineterminator = lineterminator
        self._iter = re.finditer(self.lineterminator, self.s)
        self._pos = 0

    def __next__(self):
        if self._pos is None:
            raise StopIteration

        try:
            start = self._pos
            end, self._pos = next(self._iter).span()
            return self.s[start:end]

        except StopIteration:
            start = self._pos
            self._pos = None
            return self.s[start:]

    def __iter__(self):
        return self

    class _Open:
        def __init__(self, _outer_class, fname, lineterminator):
            self._outer_class = _outer_class
            self.fname = fname
            self.lineterminator = lineterminator

        def __enter__(self):
            self.file = open(self.fname, mode="r")
            s = self.file.read()
            return self._outer_class(s, self.lineterminator)

        def __exit__(self, exc_type, exc_val, exc_tb):
            if self.file:
                self.file.close()

    @classmethod
    def open(cls, fname, lineterminator):
        return cls._Open(cls, fname, lineterminator)



if __name__ == '__main__':
    records = 'a;b;c;d;e'

    print(f"{records=}")

    print('iterating over object')
    for record in FunkyLines(records, ";"):
        print(record)

    with open('records', 'w') as f:
        f.write(records)

    print('iterating over file')
    with FunkyLines.open('records', ";") as records:
        for record in records:
            print(record)