Support for stdlib logging StreamHandler with `Live(redirect_stderr=True)`

[gusostow]

Discussed in #3280

^{Originally posted by gusostow February 15, 2024}
I want to set up a progress bar that isn't disrupted by standard logging statements. redirect_stderr is working fine when I print directly to stderr but not for logging.

Is this expected? Are there any workarounds? Ideally I wouldn't have to change the handler to RichHandler when this optional progress bar is enabled.

[github-actions]

Thank you for your issue. Give us a little time to review it.

PS. You might want to check the FAQ if you haven't done so already.

This is an automated reply, generated by FAQtory

[robinbowes]

Is this related to #2022 ?

[SebastianGrans]

Hey, I was just hitting the same issue and found a workaround.

tl;dr Inside the with Live()...-clause, you need to update the stream field of the StreamHandler instance in the logger. See the example workaround below.

Sadly, I don't think there is a clean way that this could be automatically handled by rich.

The reason why this happens is that with basicConfig, the logger is sets up a StreamHandler that logs to sys.stderr by default.

In Progress and Live, sys.stdout/sys.stderr is replaced with a FileProxy, but since StreamHandler was set up before sys.stderr was replaced, it will still print to the "regular" sys.stdout.

Minimal workaround

import logging
import sys
import time
from rich.progress import Progress
from rich.live import Live

streamhdlr = logging.StreamHandler()
logging.basicConfig(level=logging.DEBUG, handlers=[streamhdlr])
log = logging.getLogger()


with Progress(auto_refresh=False) as progress:
    task = progress.add_task("Processing...", total=100)
    streamhdlr.setStream(sys.stderr)
    for _ in range(100):
        log.info(f"Log message {_}")
        time.sleep(0.1)
        progress.update(task, advance=1)


with Live("Hello, World!", refresh_per_second=4) as live:
    streamhdlr.setStream(sys.stderr)
    for i in range(40):
        log.info("Updating live display")
        time.sleep(0.4)
        live.update(f"Count: {i}")

And it cleanly prints:

INFO:root:Log message 0
INFO:root:Log message 1
INFO:root:Log message 2
INFO:root:Log message 3
INFO:root:Log message 4
INFO:root:Log message 5
INFO:root:Log message 6
INFO:root:Log message 7
INFO:root:Log message 8
INFO:root:Log message 9
Processing... ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:00
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
INFO:root:Updating live display
Count: 9