1

给出以下简单示例：

import logging

class SmartLogRecord(logging.LogRecord):
    """ Dummy LogRecord example """

    def getMessage(self):
        return self.msg % self.args

logging.setLogRecordFactory(SmartLogRecord)

var = 'SmartLogRecord'
logging.warning('I am a %s', var)

我可以运行它Python 3并使用我的自定义LogRecord类，但Python 2会引发错误：

linux@linux-PC$ python3 text.py
WARNING:root:I am a SmartLogRecord

linux@linux-PC$ python2 text.py
Traceback (most recent call last):
  File "text.py", line 9, in <module>
    logging.setLogRecordFactory(SmartLogRecord)
AttributeError: 'module' object has no attribute 'setLogRecordFactory'

linux@linux-PC$ python3 --version
Python 3.7.2

linux@linux-PC$ python2 --version
Python 2.7.16
4

1 回答 1

2

这是setLogRecordFactory()CPython 3.7 的全部荣耀：

# https://github.com/python/cpython/blob/29500737d45cbca9604d9ce845fb2acc3f531401/Lib/logging/__init__.py#L386
_logRecordFactory = LogRecord

def setLogRecordFactory(factory):
    global _logRecordFactory
    _logRecordFactory = factory

def getLogRecordFactory():
    return _logRecordFactory

def makeLogRecord(dict):
    rv = _logRecordFactory(None, None, "", 0, "", (), None, None)
    rv.__dict__.update(dict)
    return rv

调用它的地方是 Called in Logger.makeRecord()：

def makeRecord(self, name, level, fn, lno, msg, args, exc_info,
               func=None, extra=None, sinfo=None):
    """
    A factory method which can be overridden in subclasses to create
    specialized LogRecords.
    """
    rv = _logRecordFactory(name, level, fn, lno, msg, args, exc_info, func,
                           sinfo)

相反，在 Python 2 中，这不是一件事：

# https://github.com/python/cpython/blob/7c2c01f02a1821298a62dd16ecc3a12da663e14b/Lib/logging/__init__.py#L1261
def makeRecord(self, name, level, fn, lno, msg, args, exc_info, func=None, extra=None):
    """
    A factory method which can be overridden in subclasses to create
    specialized LogRecords.
    """
    rv = LogRecord(name, level, fn, lno, msg, args, exc_info, func)

你可以做的是基本上替换对象上的.makeRecord()绑定方法Logger。换句话说：

>>> class A:
...     def f(self, a, b):
...         return a + b

>>> def new_f(self, a, b):
...     return a * b
... 
>>> A.f = new_f
>>> A().f(10, 20)
200

这看起来像：

class MyLogRecord(logging.LogRecord):
    pass
    # override stuff here

def makeRecord(self, name, level, fn, lno, msg, args, exc_info, func=None, extra=None):
        print "Using a MyLogRecord instance"
        rv = MyLogRecord(name, level, fn, lno, msg, args, exc_info, func)
        if extra is not None:
            for key in extra:
                if (key in ["message", "asctime"]) or (key in rv.__dict__):
                    raise KeyError("Attempt to overwrite %r in LogRecord" % key)
                rv.__dict__[key] = extra[key]
        return rv

logging.Logger.makeRecord = makeRecord

插图：

>>> logging.error("hello")
Using a MyLogRecord instance
ERROR:root:hello

在这种情况下，您只是根据使用单个其他MyLogRecord类的特定需求进行定制。如果你真的想要，你可以编写你自己的setLogRecordFactory()，如上所示，然后_logRecordFactory在你的替换.makeRecord()方法中使用，就像 Python 3 正在做的那样。

假设/替代（子类，不要替换）

还有一条评论：这一切都假设您想要影响logger在其他地方创建的非“您自己的”实例。如果您只想影响您自己的代码定义的记录器，您可以只子类 Logger化而不是完全替换Logger属于logging.__init__模块命名空间的类。

于 2019-05-06T01:50:43.033 回答