python：将所有错误记录到单个日志文件中

Question

我正在用 python 编写一个工具，我想把所有错误——而且只有错误——（没有按应有的计算）放到一个日志文件中。此外，我希望在我的代码的每个部分的错误日志文件中都有不同的文本，以使错误日志文件易于解释。我该如何编码？非常感谢谁能提供帮助！

Answer 1

查看python模块logging。这是一个核心模块，不仅可以在您自己的项目中统一日志记录，还可以在第三方模块中统一记录。

对于最小的日志文件示例，这直接取自the documentation：

import logging
logging.basicConfig(filename='example.log',level=logging.DEBUG)
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.warning('And this, too')

这导致example.log的内容：

DEBUG:root:This message should go to the log file
INFO:root:So should this
WARNING:root:And this, too

不过，我个人推荐使用yaml配置方式（需要pyyaml）：

#logging_config.yml

version: 1
disable_existing_loggers: False
formatters:
  standard:
    format: '%(asctime)s [%(levelname)s] %(name)s - %(message)s'
handlers:
  console:
    class: logging.StreamHandler
    level: INFO
    formatter: standard
    stream: ext://sys.stdout
  file:
    class: logging.FileHandler
    level: DEBUG
    formatter: standard
    filename: output.log
  email:
    class: logging.handlers.SMTPHandler
    level: WARNING
    mailhost: smtp.gmail.com
    fromaddr: to@address.co.uk
    toaddrs: to@address.co.uk
    subject: Oh no, something's gone wrong!
    credentials: [email, password]
    secure: []
root:
  level: DEBUG
  handlers: [console, file, email]
  propagate: True

然后使用，例如：

import logging.config
import yaml

with open('logging_config.yml', 'r') as config:
    logging.config.dictConfig(yaml.safe_load(config))

logger = logging.getLogger(__name__)

logger.info("This will go to the console and the file")
logger.debug("This will only go to the file")
logger.error("This will go everywhere")

try:
    list = [1, 2, 3]
    print(list[10])
except IndexError:
    logger.exception("This will also go everywhere")

打印出来：

2018-07-18 13:29:21,434 [INFO] __main__ - This will go to the console and the file
2018-07-18 13:29:21,434 [ERROR] __main__ - This will go everywhere
2018-07-18 13:29:21,434 [ERROR] __main__ - This will also go everywhere
Traceback (most recent call last):
  File "C:/Users/Chris/Desktop/python_scratchpad/a.py", line 16, in <module>
    print(list[10])
IndexError: list index out of range

虽然日志文件的内容是：

2018-07-18 13:35:55,423 [INFO] __main__ - This will go to the console and the file
2018-07-18 13:35:55,424 [DEBUG] __main__ - This will only go to the file
2018-07-18 13:35:55,424 [ERROR] __main__ - This will go everywhere
2018-07-18 13:35:55,424 [ERROR] __main__ - This will also go everywhere
Traceback (most recent call last):
  File "C:/Users/Chris/Desktop/python_scratchpad/a.py", line 15, in <module>
    print(list[10])
IndexError: list index out of range

当然，您可以添加或删除处理程序、格式化程序等，或在代码中执行所有这些操作（请参阅 Python 文档），但这是我在项目中使用日志记录时的起点。我发现在专用配置文件中进行配置而不是通过在代码中定义日志来污染我的项目是很有帮助的。