[英]How to capture the output on stderr of a logger using a StreamHandler?
Redirecting the output of normal logging works fine: 重定向正常日志记录的输出工作正常:
import contextlib
import io
import logging
std_out_capture = io.StringIO()
with contextlib.redirect_stderr(std_out_capture):
logging.error('Hi.')
output = std_out_capture.getvalue()
print(f'output: {output}')
output: 输出:
output: ERROR:root:Hi.
However when changing the log format using logging.basicConfig
但是,使用
logging.basicConfig
更改日志格式时
import contextlib
import io
import logging
log_format = '[%(threadName)s] [%(levelname)s] %(message)s'
logging.basicConfig(format=log_format)
std_out_capture = io.StringIO()
with contextlib.redirect_stderr(std_out_capture):
logging.error('Hi.')
output = std_out_capture.getvalue()
print(f'output: {output}')
the output is: 输出是:
output:
[MainThread] [ERROR] Hi.
So the output is not captured any more. 因此不再捕获输出。
My guess is this is because 我猜这是因为
logging.basicConfig(**kwargs): Does basic configuration for the logging system by creating a StreamHandler with a default Formatter and adding it to the root logger.
logging.basicConfig(** kwargs):通过使用默认Formatter创建StreamHandler并将其添加到根记录器来为日志记录系统进行基本配置。
( https://docs.python.org/3/library/logging.html#logging.basicConfig ) ( https://docs.python.org/3/library/logging.html#logging.basicConfig )
and StreamHandler
is working in a separate thread, so it's output is not captured. 和
StreamHandler
在一个单独的线程中工作,因此不会捕获它的输出。
For unit testing I would like to capture it anyways. 对于单元测试,我想要捕获它。 How can I do this?
我怎样才能做到这一点?
You'll have to pull the logging configuration into the with
statement-body so StreamHandler
already gets initialized with the altered stderr
: 您必须将日志记录配置拉入
with
statement-body,因此StreamHandler
已经使用更改的stderr
进行初始化:
import contextlib
import io
import logging
std_out_capture = io.StringIO()
with contextlib.redirect_stderr(std_out_capture):
log_format = '[%(threadName)s] [%(levelname)s] %(message)s'
logging.basicConfig(format=log_format)
logging.error('Hi.')
output = std_out_capture.getvalue()
print(f'output: {output}')
# output: [MainThread] [ERROR] Hi.
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