The syntax to colorize the log message

[Pandede]

I'm wondering if there is any method to colorize the log message? For example, in loguru:

from loguru import logger

color_logger = logger.opt(colors=True)
color_logger.info("This is a <blue>message</>")

[trim21]

you mayneed to use colorma and add color to message by yourself， don't think structlog support this

[hynek]

structlog defines a bunch of color codes for its own use:

https://github.com/hynek/structlog/blob/b265c7acbb700f7483f59b70c58855e59d9fc232/src/structlog/dev.py#L90-L103

So this is really easy with f-strings: logger.info(f"This is a {BLUE}message{RESET_ALL}.") and you don't need special syntax. Colorama is only necessary on Windows.

There's been some plans to deepen the integration with Rich and allow for its codes but since structlog's focus remains production systems, it hasn't become a priority yet.

[Pandede]

@hynek This wordaround is pretty implicit, should it be considered as a precessor? Just like KeyValueRenderer.

[hynek]

Processors are always a great idea! If you want the colors only in the event (and not the keys) it would be even trivial to implement since you would only have to replace strings with other strings.

Replacing a whole renderer is a bit more involved.

[Pandede]

Thanks for the quick response! I just follows the tutorial to create a custom KeyValueColumnFormatter:

from dataclasses import dataclass
from io import StringIO
from typing import Literal

from rich.console import Console

import structlog
from structlog.dev import Column

@dataclass
class RichColumnFormatter:
    color_system: Literal[
        "auto", "standard", "256", "truecolor", "windows"
    ] = "truecolor"
    emoji: bool | None = None
    markup: bool | None = None
    highlight: bool | None = None

    def __call__(self, key: str, value: object) -> str:
        with StringIO() as sio:
            Console(file=sio, color_system=self.color_system).print(
                value,
                emoji=self.emoji,
                markup=self.markup,
                highlight=self.highlight,
                end="",
            )
            return sio.getvalue()

def get_column_index(columns: list[Column], key: str) -> int:
    for i, c in enumerate(columns):
        if c.key == key:
            return i
    raise ValueError("No column found for key: {}".format(key))

# Replace the column formatter for the "event" column
cr = structlog.dev.ConsoleRenderer()
event_column_index = get_column_index(cr._columns, "event")
cr._columns[event_column_index].formatter = RichColumnFormatter()

# Follow the instructions in this tutorial
# https://www.structlog.org/en/stable/console-output.html#console-output-configuration
structlog.configure(
    processors=structlog.get_config()["processors"][:-1] + [cr]
)
logger: structlog.stdlib.BoundLogger = structlog.get_logger()

if __name__ == "__main__":
    logger.info("[blue]Hello, World![/]", foo=1, bar=2)

I'll close the issue with the workaround.