problem with interpolation and logging.config.dictConfig with python3.6+

[Tim Williams]

I'm having a problem using configobj with interpolation to configure a logger. Everything works fine with python3.4, python3.5, but for python3.5 and above, I get an exception.

Here is my test program:

import sys
import configobj
import logging, logging.config

msg = '***** python version: \n{}\n*****\n'.format(sys.version)
print(msg)

config = configobj.ConfigObj('logtest.ini')
# make version an int
config['logging']['version'] = int(config['logging']['version'])
logging.config.dictConfig(config['logging'])
logger=logging.getLogger('root')
logger.info(msg)

and my INI file:

[logging]
	version = 1
	level = INFO
	[[formatters]]
		[[[fmt1]]]
			format = %(asctime)s: (%(levelname)s)	%(message)s
	[[handlers]]
		[[[console]]]
			class = logging.StreamHandler
			level = INFO
			stream = ext://sys.stderr
			formatter = fmt1
		[[[file]]]
			class = logging.FileHandler
			level = INFO
			mode = a
			formatter = fmt1
			filename = test.log
	[[loggers]]
		[[[root]]]
			level = INFO
			handlers = console, file

running under python3.4 or python 3.5:

(py36) C:\Users\Tim\workspace\CollectionSoftware>conda.bat activate py35

(py35) C:\Users\Tim\workspace\CollectionSoftware>python testlogging.py
***** python version:
3.5.5 | packaged by conda-forge | (default, Jul 24 2018, 01:52:17) [MSC v.1900 64 bit (AMD64)]

---

2019-09-29 12:53:27,027: (INFO) ***** python version:
3.5.5 | packaged by conda-forge | (default, Jul 24 2018, 01:52:17) [MSC v.1900 64 bit (AMD64)]

---

But when I try the same program with python3.6, I get a ValueError when trying to configer my logger format:

(py35) C:\Users\Tim\workspace\CollectionSoftware>conda.bat activate py36

(py36) C:\Users\Tim\workspace\CollectionSoftware>python testlogging.py
***** python version:
3.6.7 (default, Jul 2 2019, 02:21:41) [MSC v.1900 64 bit (AMD64)]

---

Traceback (most recent call last):
File "C:\Users\Tim\Miniconda3\envs\py36\lib\logging\config.py", line 545, in configure
formatters[name])
File "C:\Users\Tim\Miniconda3\envs\py36\lib\logging\config.py", line 327, in getitem
return self.convert_with_key(key, value)
File "C:\Users\Tim\Miniconda3\envs\py36\lib\logging\config.py", line 293, in convert_with_key
result = self.configurator.convert(value)
File "C:\Users\Tim\Miniconda3\envs\py36\lib\logging\config.py", line 446, in convert
value = ConvertingDict(value)
File "C:\Users\Tim\Miniconda3\envs\py36\lib\site-packages\configobj.py", line 557, in getitem
return self._interpolate(key, val)
File "C:\Users\Tim\Miniconda3\envs\py36\lib\site-packages\configobj.py", line 549, in _interpolate
return engine.interpolate(key, value)
File "C:\Users\Tim\Miniconda3\envs\py36\lib\site-packages\configobj.py", line 352, in interpolate
value = recursive_interpolate(key, value, self.section, {})
File "C:\Users\Tim\Miniconda3\envs\py36\lib\site-packages\configobj.py", line 330, in recursive_interpolate
k, v, s = self._parse_match(match)
File "C:\Users\Tim\Miniconda3\envs\py36\lib\site-packages\configobj.py", line 417, in _parse_match
value, section = self._fetch(key)
File "C:\Users\Tim\Miniconda3\envs\py36\lib\site-packages\configobj.py", line 386, in _fetch
raise MissingInterpolationOption(key)
configobj.MissingInterpolationOption: missing option "asctime" in interpolation.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "testlogging.py", line 11, in
logging.config.dictConfig(config['logging'])
File "C:\Users\Tim\Miniconda3\envs\py36\lib\logging\config.py", line 802, in dictConfig
dictConfigClass(config).configure()
File "C:\Users\Tim\Miniconda3\envs\py36\lib\logging\config.py", line 548, in configure
'formatter %r: %s' % (name, e))
ValueError: Unable to configure formatter 'fmt1': missing option "asctime" in interpolation.

It could be a bug in logging.config, but I'm thinking it may be somewhere in configobj.interpolate()

Thanks for any help

[Tim Williams]

I think the source my confusion is that the formatting of the logging module LogRecord attributes Is identical to the 'ConfigParser' interpolation.
I changed the interpolation to 'Template', then made sure to change the confiobj key values to have that format, while leaving the format statement alone, e.g.

[MainWindow]
	NumCameras = 1
	RootDir = TestData
	CaptureDrive = "C:/"
	LogFile = ${CaptureDrive}${RootDir)/test.log

[logging]
	version = 1
	level = INFO
	[[formatters]]
		[[[fmt1]]]
			format = %(asctime)s: (%(levelname)s)	%(message)s
			datefmt = 
	[[handlers]]
		[[[console]]]
			class = logging.StreamHandler
			level = INFO
			stream = ext://sys.stderr
			formatter = fmt1
		[[[file]]]
			class = logging.FileHandler
			level = INFO
			mode = a
			formatter = fmt1
			filename = C:/TestData/test_20190530.log
	[[loggers]]
		[[[root]]]
			level = INFO
			handlers = console, file