[feature] Multi line output and multi log lines

[ddofborg]

When dealing with multi line output, like with log.info("This is\nsecond line and\nthird line and\nfouth line") it would be great if the output in the logs would be split for better readability. In this case the 'connected' lines are prefixed by a +---+ to see they are all one message.

Code:

log.info("test")
log.info("This is\nsecond line and\nthird line and\nfouth line")
log.info("test")

Output:

2025-08-09 07:53:37 [INFO    ] test [suffix]
2025-08-09 07:53:37 [INFO    ] + This is [suffix]
2025-08-09 07:53:37 [INFO    ] | second line and [suffix]
2025-08-09 07:53:37 [INFO    ] | third line and [suffix]
2025-08-09 07:53:37 [INFO    ] + fouth line [suffix]
2025-08-09 07:53:37 [INFO    ] test [suffix]

What do you think?

[Delgan]

Hi.

This is a request that comes up from time to time, always with different formatting specificities. However, Loguru deliberately avoids manipulating the logged message for simplicity and consistency. In my opinion, dividing a message into multiple lines using the same prefixed format may lead the reader to mistakenly interpret it as multiple logging function calls, when in reality only a single call was made. For this reason, I prefer Loguru to straightforwardly display the message as is.

But again, if you want, you can use a custom formatter:

from loguru import logger
import sys


def multiline_formatter(record):
    message = record["message"]

    if "\n" not in message:
        return "[{time}] [{level:<8}] {message}\n{exception}"

    lines = message.split("\n")
    format_lines = []

    for i, line in enumerate(lines):
        prefix = "|" if 0 < i < len(lines) - 1 else "+"
        format_line = "[{time}] [{level:<8}] %s {extra[lines][%d]}" % (prefix, i)
        format_lines.append(format_line)

    record["extra"]["lines"] = lines

    return "\n".join(format_lines) + "\n{exception}"


logger.remove()
logger.add(sys.stderr, format=multiline_formatter, level="DEBUG")

logger.info("test")
logger.info("This is\nsecond line and\nthird line and\nfouth line")
logger.info("test")