logging.StreamHandler(stream=sys.stdout)

logging.StreamHandler(stream=sys.stdout) 是一个用于将日志消息输出到标准输出流（即控制台）的处理器（handler）。其中 stream 参数指定了要输出到的流，sys.stdout 表示标准输出流。当有一个日志消息传递给处理器时，该处理器将会将消息输出到指定的流中。logging.StreamHandler() 方法还可以接受其他参数，例如 level、formatter 等，用于指定处理器的日志级别和消息格式。

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logging.StreamHandler(stream=_streams[stream])

logging.StreamHandler(stream=_streams[stream]) 是一个用于将日志消息输出到流（stream）的处理器（handler）。其中 stream 参数指定了要输出到的流，_streams 参数是 Python 内置的字典，表示支持的流类型及其对应的标识符。例如，当 stream 参数为 sys.stdout 时，表示将日志消息输出到标准输出流（即控制台）。同样地，当 stream 参数为 sys.stderr 时，表示将日志消息输出到标准错误流。logging.StreamHandler() 方法还可以接受其他参数，例如 level、formatter 等，用于指定处理器的日志级别和消息格式。

logging.StreamHandler

`logging.StreamHandler` is a class in the Python `logging` module that sends logging output to a stream (e.g. `sys.stdout`, `sys.stderr`, or a file-like object). It can be used to configure logging to send output to the console or to a file.

Here's an example of how to use it:

import logging

# Create a logger
logger = logging.getLogger('example_logger')
logger.setLevel(logging.DEBUG)

# Create a stream handler and set its logging level to INFO
stream_handler = logging.StreamHandler()
stream_handler.setLevel(logging.INFO)

# Add the stream handler to the logger
logger.addHandler(stream_handler)

# Log some messages
logger.debug('Debug message')
logger.info('Info message')
logger.warning('Warning message')
logger.error('Error message')
logger.critical('Critical message')

In this example, `logging.StreamHandler` is used to send logging output to the console. The `logger` object is created with a name of `'example_logger'` and its logging level is set to `DEBUG`. A stream handler is created with a logging level of `INFO`, which means that it will only handle messages with a severity level of `INFO` or higher. The stream handler is added to the logger, and then several messages are logged at different severity levels. Since the logger's logging level is set to `DEBUG`, all messages are processed by the logger and sent to the stream handler. The stream handler only outputs messages with a severity level of `INFO` or higher, so only the `INFO`, `WARNING`, `ERROR`, and `CRITICAL` messages are displayed on the console.