在Python记录器中覆盖Lineno的最佳方法 [英] Best way to override lineno in Python logger

问题描述

我写了一个装饰器，记录了用于调用特定函数或方法的参数.如下所示，它工作得很好，除了logRecord中报告的行号是装饰器的行号，而不是要包装的func的行号:

I have written a decorator which logs the arguments used to call a particular function or method. As shown below, it works well except that the line number reported in the logRecord is the line number of the decorator rather than the line number of func that is being wrapped:

from functools import wraps
import inspect
import logging

arg_log_fmt = "{name}({arg_str})"


def log_args(logger, level=logging.DEBUG):
    """Decorator to log arguments passed to func."""
    def inner_func(func):
        line_no = inspect.getsourcelines(func)[-1]

        @wraps(func)
        def return_func(*args, **kwargs):
            arg_list = list("{!r}".format(arg) for arg in args)
            arg_list.extend("{}={!r}".format(key, val)
                            for key, val in kwargs.iteritems())
            msg = arg_log_fmt.format(name=func.__name__,
                                     arg_str=", ".join(arg_list))
            logger.log(level, msg)
            return func(*args, **kwargs)
        return return_func

    return inner_func

if __name__ == "__main__":
    logger = logging.getLogger(__name__)
    handler = logging.StreamHandler()
    fmt = "%(asctime)s %(levelname)-8.8s [%(name)s:%(lineno)4s] %(message)s"
    handler.setFormatter(logging.Formatter(fmt))
    logger.addHandler(handler)
    logger.setLevel(logging.DEBUG)


    @log_args(logger)
    def foo(x, y, z):
        pass

    class Bar(object):
        @log_args(logger)
        def baz(self, a, b, c):
            pass

    foo(1, 2, z=3)
    foo(1, 2, 3)
    foo(x=1, y=2, z=3)

    bar = Bar()
    bar.baz(1, c=3, b=2)

此示例将产生以下输出

2015-09-07 12:42:47,779 DEBUG    [__main__:  25] foo(1, 2, z=3)
2015-09-07 12:42:47,779 DEBUG    [__main__:  25] foo(1, 2, 3)
2015-09-07 12:42:47,779 DEBUG    [__main__:  25] foo(y=2, x=1, z=3)
2015-09-07 12:42:47,779 DEBUG    [__main__:  25] baz(<__main__.Bar object at 0x1029094d0>, 1, c=3, b=2)

请注意，所有行号均指向装饰器.

Note that the line numbers all point to the decorator.

使用inspect.getsourcelines(func)可以获取我感兴趣的行号，但是尝试覆盖logger.debug中的lineno会导致错误.使包装函数的行号出现在日志记录语句中的最佳方法是什么?

With inspect.getsourcelines(func) I can get the line number I'm interested in, but an attempt to over-write lineno in logger.debug results in an error. What is the best approach to getting the line number of the wrapped function to appear in the logging statement?

推荐答案

正如Martijn指出的那样，事情有时会发生变化.但是，由于您使用的是Python 2(迭代器已将其放弃)，因此如果您不介意猴子修补日志记录，则以下代码将起作用:

As Martijn points out, things sometimes change. However, since you're using Python 2 (the iteritems gave it away), the following code will work if you don't mind monkey-patching logging:

from functools import wraps
import logging

class ArgLogger(object):
    """
    Singleton class -- will only be instantiated once
    because of the monkey-patching of logger.
    """

    singleton = None

    def __new__(cls):
        self = cls.singleton
        if self is not None:
            return self
        self = cls.singleton = super(ArgLogger, cls).__new__(cls)
        self.code_location = None

        # Do the monkey patch exactly one time
        def findCaller(log_self):
            self.code_location, code_location = None, self.code_location
            if code_location is not None:
                return code_location
            return old_findCaller(log_self)
        old_findCaller = logging.Logger.findCaller
        logging.Logger.findCaller = findCaller

        return self

    def log_args(self, logger, level=logging.DEBUG):
        """Decorator to log arguments passed to func."""
        def inner_func(func):
            co = func.__code__
            code_loc = (co.co_filename, co.co_firstlineno, co.co_name)

            @wraps(func)
            def return_func(*args, **kwargs):
                arg_list = list("{!r}".format(arg) for arg in args)
                arg_list.extend("{}={!r}".format(key, val)
                                for key, val in kwargs.iteritems())
                msg = "{name}({arg_str})".format(name=func.__name__,
                                        arg_str=", ".join(arg_list))
                self.code_location = code_loc
                logger.log(level, msg)
                return func(*args, **kwargs)
            return return_func

        return inner_func


log_args = ArgLogger().log_args

if __name__ == "__main__":
    logger = logging.getLogger(__name__)
    handler = logging.StreamHandler()
    fmt = "%(asctime)s %(levelname)-8.8s [%(name)s:%(lineno)4s] %(message)s"
    handler.setFormatter(logging.Formatter(fmt))
    logger.addHandler(handler)
    logger.setLevel(logging.DEBUG)


    @log_args(logger)
    def foo(x, y, z):
        pass

    class Bar(object):
        @log_args(logger)
        def baz(self, a, b, c):
            pass

    def test_regular_log():
        logger.debug("Logging without ArgLog still works fine")

    foo(1, 2, z=3)
    foo(1, 2, 3)
    foo(x=1, y=2, z=3)

    bar = Bar()
    bar.baz(1, c=3, b=2)
    test_regular_log()

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