8000 Attribute `handlers` is empty after using `basicConfig` or `dictConfig` · Issue #107515 · python/cpython · GitHub
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hundredball opened this issue Jul 31, 2023 · 2 comments
Closed
2 tasks done

Attribute handlers is empty after using basicConfig or dictConfig #107515

hundredball opened this issue Jul 31, 2023 · 2 comments
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@vsajip
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invalid stdlib Python modules in the Lib dir

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@hundredball
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hundredball commented Jul 31, 2023 •
edited by hugovk
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Bug report

Checklist

  • I am confident this is a bug in CPython,
    not a bug in a third-party project
  • I have searched the CPython issue tracker,
    and am confident this bug has not been reported before

A clear and concise description of the bug

After using basicConfig or dictConfig for a logger, handlers attribute would still be [] while hasHandlers equals True. Even though handlers is empty, StreamHandler still works and prints out log messages.

Code:

import logging
import logging.config

basic_logger = logging.getLogger("basic")
print(f"hasHandlers: {basic_logger.hasHandlers()}, handlers: {basic_logger.handlers}")
basic_logger.error("1")

logging.basicConfig(level=logging.INFO)
print(f"hasHandlers: {basic_logger.hasHandlers()}, handlers: {basic_logger.handlers}")
basic_logger.error("2")

config = {
    "version": 1.0,
    "handlers": {
        "console": {
            "class": "logging.StreamHandler",
            "level": "DEBUG",
            "stream": "ext://sys.stdout"
        }
    },
    "root": {
        "level": "DEBUG",
        "handlers": ["console"]
    }
}
logging.config.dictConfig(config)
dict_logger = logging.getLogger("dict")
print(f"hasHandlers: {dict_logger.hasHandlers()}, handlers: {dict_logger.handlers}")
dict_logger.error("3")

Output:

hasHandlers: False, handlers: []
hasHandlers: True, handlers: []
hasHandlers: True, handlers: []
3
1
ERROR:basic:2

Your environment

  • CPython versions tested on: Python 3.9.16
  • Operating system and architecture: MacOS Monterey 12.6.1
@hundredball hundredball added the type-bug An unexpected behavior, bug, or error label Jul 31, 2023
@AlexWaygood AlexWaygood added the stdlib Python modules in the Lib dir label Jul 31, 2023
@hugovk hugovk mentioned this issue Aug 1, 2023
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@vsajip vsajip added invalid and removed type-bug An unexpected behavior, bug, or error labels Aug 1, 2023
@vsajip
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vsajip commented Aug 1, 2023

The documentation for hasHandlers{} says:

Checks to see if this logger has any handlers configured.

This is done by looking for handlers in this logger and its parents in the logger hierarchy.

Returns True if a handler was found, else False.

The method stops searching up the hierarchy whenever a logger with the ‘propagate’ attribute
set to false is found - that will be the last logger which is checked for the existence of handlers.

From this, it should be clear that the result of hasHandlers() for a logger is only partly determined by the contents of that logger's handlers attribute.

Before asserting that "I am confident this is a bug in CPython", please view the available documentation and perhaps ask on discuss.python.org, Stack Overflow etc. to confirm that others agree there's a problem there to be addressed.

@vsajip vsajip closed this as not planned Won't fix, can't repro, duplicate, stale Aug 1, 2023
@hundredball
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Hi @vsajip, thanks for the explanation. I realized that handlers are actually in the parent of logger and I can access them now.

Sorry for the confusion 😔

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