Evaluate statements from within Python logging YAML config file -

consider following snippet of python logging yaml config file:

version: 1 formatters:   simple:     format: '%(asctime)s - %(name)s - %(levelname)s - %(message)s' handlers:   logfile:     class: logging.handlers.timedrotatingfilehandler     level: debug     filename: some_fancy_import_name.generate_filename_called_error     backupcount: 5     formatter: simple 

i load yaml config file way:

with open('logging.yaml', 'r') fd:     config = yaml.safe_load(fd.read()) logging.config.dictconfig(config) 

take special notice of filename handler should write logs. in normal python code, expect some_fancy_import_name.generate_filename_called_errorlog generate string 'error.log'. in all, logging handler should write file 'error.log' in current directory.

however, turns out, not case. when @ current directory, see file named 'some_fancy_import_name.generate_filename_called_errorlog'.

why go through trouble?

i filename programmatically determined. have tried configuring logging using normal python scripting way:

# fancy import name os import environ env  # programmatically determine filename path log_location = env.get('openshift_log_dir', '.') log_filename = os.path.join(log_location, 'error') handler = logging.handlers.timedrotatingfilehandler(log_filename) 

see how log_filename path inferred environment variables.

i translate yaml config file. possible?

perhaps might need dig through dict produced yaml.safe_load(fd.read()) , eval() stuff?

you can add custom constructor , mark value special tag, constructor gets executed when loading it:

import yaml  def eval_constructor(loader, node):   return eval(loader.construct_scalar(node))  yaml.add_constructor(u'!eval', eval_constructor)  some_value = '123'  config = yaml.load(""" version: 1 formatters:   simple:     format: '%(asctime)s - %(name)s - %(levelname)s - %(message)s' handlers:   logfile:     class: logging.handlers.timedrotatingfilehandler     level: debug     filename: !eval some_value     backupcount: 5     formatter: simple """)  print config['handlers']['logfile']['filename'] 

this prints 123, since value some_value has tag !eval, , therefore loaded eval_constructor.

be aware of security implications of evaling configuration data. arbitrary python code can executed writing yaml file!