Reading a file with a specified delimiter for newline

Question

I have a file in which lines are separated using a delimeter say .. I want to read this file line by line, where lines should be based on presence of .

Answer 1

Here is a more efficient answer, using FileIO and bytearray that I used for parsing a PDF file -

import io
import re


# the end-of-line chars, separated by a `|` (logical OR)
EOL_REGEX = b'\r\n|\r|\n'  

# the end-of-file char
EOF = b'%%EOF'



def readlines(fio):
    buf = bytearray(4096)
    while True:
        fio.readinto(buf)
        try:
            yield buf[: buf.index(EOF)]
        except ValueError:
            pass
        else:
            break
        for line in re.split(EOL_REGEX, buf):
            yield line


with io.FileIO("test.pdf") as fio:
    for line in readlines(fio):
        ...

The above example also handles a custom EOF. If you don't want that, use this:

import io
import os
import re


# the end-of-line chars, separated by a `|` (logical OR)
EOL_REGEX = b'\r\n|\r|\n'  


def readlines(fio, size):
    buf = bytearray(4096)
    while True:
        if fio.tell() >= size:
            break               
        fio.readinto(buf)            
        for line in re.split(EOL_REGEX, buf):
            yield line

size = os.path.getsize("test.pdf")
with io.FileIO("test.pdf") as fio:
    for line in readlines(fio, size):
         ...