Python: How to Create an Exception Logging Decorator

exception_decor.py

import functools
import logging
 
def create_logger():
    """
    Creates a logging object and returns it
    """
    logger = logging.getLogger("example_logger")
    logger.setLevel(logging.INFO)
 
    # create the logging file handler
    fh = logging.FileHandler("/path/to/test.log")
 
    fmt = '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
    formatter = logging.Formatter(fmt)
    fh.setFormatter(formatter)
 
    # add handler to logger object
    logger.addHandler(fh)
    return logger
 
 
def exception(function):
    """
    A decorator that wraps the passed in function and logs 
    exceptions should one occur
    """
    @functools.wraps(function)
    def wrapper(*args, **kwargs):
        logger = create_logger()
        try:
            return function(*args, **kwargs)
        except:
            # log the exception
            err = "There was an exception in  "
            err += function.__name__
            logger.exception(err)
 
            # re-raise the exception
            raise
    return wrapper

在该代码中，有两个函数。第一个函数创建了日志对象并返回该日志对象。第二个函数是我们的装饰器函数。我们在一个try/except中封装传递的函数，当logger中发生任何异常的时候，进行日志记录。并且我还记录了当异常发生时的函数名称。

现在让我们测试下该装饰器。

    from exception_decor import exception
     
    @exception
    def zero_divide():
        1 / 0
     
    if __name__ == '__main__':
        zero_divide()

运行以上测试代码后，会出现以下错误日志：

2016-06-09 08:26:50,874 - example_logger - ERROR - There was an exception in  zero_divide
Traceback (most recent call last):
  File "/home/mike/exception_decor.py", line 29, in wrapper
    return function(*args, **kwargs)
  File "/home/mike/test_exceptions.py", line 5, in zero_divide
    1 / 0
ZeroDivisionError: integer division or modulo by zero

传递一个 logger 到装饰器

# exception_logger.py
 
import logging
 
def create_logger():
    """
    Creates a logging object and returns it
    """
    logger = logging.getLogger("example_logger")
    logger.setLevel(logging.INFO)
 
    # create the logging file handler
    fh = logging.FileHandler(r"/path/to/test.log")
 
    fmt = '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
    formatter = logging.Formatter(fmt)
    fh.setFormatter(formatter)
 
    # add handler to logger object
    logger.addHandler(fh)
    return logger
 
logger = create_logger()

现在修改前面出现的装饰器，以便可以接受 logger 作为参数。

# exception_decor.py
 
import functools
 
 
def exception(logger):
    """
    A decorator that wraps the passed in function and logs 
    exceptions should one occur
 
    @param logger: The logging object
    """
 
    def decorator(func):
 
        def wrapper(*args, **kwargs):
            try:
                return func(*args, **kwargs)
            except:
                # log the exception
                err = "There was an exception in  "
                err += func.__name__
                logger.exception(err)
 
            # re-raise the exception
            raise
        return wrapper
    return decorator

最后修改测试脚本：

from exception_decor import exception
from exception_logger import logger
 
@exception(logger)
def zero_divide():
    1 / 0
 
if __name__ == '__main__':
    zero_divide()