我尝试在使用两个记录器对象之前和之后使用打印函数,将输出流式传输到控制台。 问题是我得到的输出非常困惑,不符合预期的顺序。
我尝试将 print() 更改为 logger_object.info(),它按预期工作得很好。
具有意外输出的完整代码:
import logging
# Create logger objects and set level
loggerA = logging.getLogger()
loggerA.setLevel(logging.DEBUG)
loggerB = logging.getLogger()
loggerB.setLevel(logging.DEBUG)
# Set log output format
log_format = logging.Formatter('%(asctime)s - %(levelname)s - %(name)s - %(message)s', datefmt='%m/%d/%Y - %I:%M:%S %p')
# Create a console stream handler
stream_handler = logging.StreamHandler()
stream_handler.setFormatter(log_format)
# Add handlers to the loggers
loggerA.addHandler(stream_handler)
loggerB.addHandler(stream_handler)
def main():
for i in range(10):
print('Starting loop number {}'.format(i))
loggerA.info("loop number {}".format(i))
loggerB.info("loop number {}".format(i))
print('Finished loop number {}'.format(i))
if __name__ == '__main__':
main()
添加 loggerC 对象以用 loggerC.info() 替换 print() :
...
loggerC = logging.getLogger()
loggerC.setLevel(logging.DEBUG)
...
def main():
for i in range(10):
loggerC('Starting loop number {}'.format(i))
loggerA.info("loop number {}".format(i))
loggerB.info("loop number {}".format(i))
loggerC('Finished loop number {}'.format(i))
...
使用 print() 意外输出的第一种情况是:
04/06/2019 - 10:10:34 AM - INFO - loggerA - loop number 1
Starting loop number 1
04/06/2019 - 10:10:34 AM - INFO - loggerB - loop number 1
04/06/2019 - 10:10:34 AM - INFO - loggerA - loop number 2
04/06/2019 - 10:10:34 AM - INFO - loggerB - loop number 2
Finished loop number 1
Starting loop number 2
Finished loop number 2
Starting loop number 3
Finished loop number 3
04/06/2019 - 10:10:34 AM - INFO - loggerA - loop number 3
04/06/2019 - 10:10:34 AM - INFO - loggerB - loop number 3
第二种情况使用 loggerC.info() 而不是 print(),这是预期的输出:
04/06/2019 - 10:12:21 AM - INFO - loggerC - Starting loop number 1
04/06/2019 - 10:12:21 AM - INFO - loggerA - loop number 1
04/06/2019 - 10:12:21 AM - INFO - loggerB - loop number 1
04/06/2019 - 10:12:21 AM - INFO - loggerC - Finished loop number 1
04/06/2019 - 10:12:21 AM - INFO - loggerC - Starting loop number 2
04/06/2019 - 10:12:21 AM - INFO - loggerA - loop number 2
04/06/2019 - 10:12:21 AM - INFO - loggerB - loop number 2
04/06/2019 - 10:12:21 AM - INFO - loggerC - Finished loop number 2
04/06/2019 - 10:12:21 AM - INFO - loggerC - Starting loop number 3
04/06/2019 - 10:12:21 AM - INFO - loggerA - loop number 3
04/06/2019 - 10:12:21 AM - INFO - loggerB - loop number 3
04/06/2019 - 10:12:21 AM - INFO - loggerC - Finished loop number 3
最佳答案
您的问题可能是 standard streams 的问题。默认情况下,print
使用std::out
,logger.info
使用std::err
。两个流are bound to your terminal但它们可能有不同的flush
刷新或触发器。
这就是为什么你的输出混合在一起,函数写入不同的流,并且它们以不同的方式刷新到终端,导致明显不一致的结果。
更改您的第一个代码以强制 logger.info
使用与 print
相同的流解决您的问题:
import sys
stream_handler = logging.StreamHandler(sys.stdout)
现在,它返回正确的输出:
-- Starting loop number 0
04/06/2019 - 07:41:34 AM - INFO - root - loop number 0
04/06/2019 - 07:41:34 AM - INFO - root - loop number 0
-- Finished loop number 0
-- Starting loop number 1
04/06/2019 - 07:41:34 AM - INFO - root - loop number 1
04/06/2019 - 07:41:34 AM - INFO - root - loop number 1
-- Finished loop number 1
-- Starting loop number 2
04/06/2019 - 07:41:34 AM - INFO - root - loop number 2
04/06/2019 - 07:41:34 AM - INFO - root - loop number 2
-- Finished loop number 2
-- Starting loop number 3
04/06/2019 - 07:41:34 AM - INFO - root - loop number 3
04/06/2019 - 07:41:34 AM - INFO - root - loop number 3
-- Finished loop number 3
因为 print
和 logger.info
每当将其刷新到终端时都会以正确的顺序提供相同的流,因此结果是正确的。
您还可以保留different streams并强制 std::out
流为 flushed explicitly :
def main():
for i in range(10):
print('-- Starting loop number {}'.format(i))
# Force std::out stream (fed by print) to be flushed to the terminal
# before logger feeds std::err and also flushes
sys.stdout.flush()
loggerA.info("loop number {}".format(i))
loggerB.info("loop number {}".format(i))
print('-- Finished loop number {}'.format(i))
sys.stdout.flush()
第二个版本也产生了预期的结果。
还要记住logger
的定义是thread-safe但 print
不是。如果您要使用线程创建模块,只需使用logger
来跟踪执行情况。
关于python - 为什么 print() 和 logger 对象以意外的顺序流式传输到控制台输出?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/55546757/