Question

Let’s say I have a logging setup like this in my Python script:

import logging

logging.basicConfig(level=logging.DEBUG, stream=sys.stdout,
                    format='%(asctime)s %(levelname)s %(message)s',
                    datefmt='%a, %d %b %Y %H:%M:%S')
logging.info('info')
logging.error('error...')
logging.debug('debug...')

Is there a way I can have it wait to print to stdout until the script is finished running and sort the log messages by level before printing?

Answer 1

From the looks of it, the object passed to stream only needs to have a write method. This means you can create a list-like object which appends data when write is called — You can then sort the list-like object trivially before printing.

import logging

class LogList(list):
   def write(self,data):
       self.append(data)

LL = LogList()
logging.basicConfig(stream = LL,level=logging.DEBUG)
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.error('Wow, this is bad')
logging.warning('And this, too')
logging.debug('foobar')
logging.warning('baz')

for line in sorted(LL):
   print line[:-1]

Of course, you might need to make your sort key a little more to pick up different levels. Something like:

levels = {'DEBUG':0,'INFO':1,'WARNING':2,'ERROR':3}
LL.sort(key = lambda x: levels[x.split(':')[0]])