python variable sharing between packages/modules

Question

trying to understand and learn how to write packages... testing with something i\'ve always used, logging...

Can you please help me understand why the \'log\' variable i

Answer 1

log is a global variable in the differentlogging module. Thus you can access it as clusterlogging.differentlogging.log.

You could also do something like from clusterlogging.differentlogging import log and then access it as just log.

Edit: actually, on reviewing your code again I don't know what to make of it. Could you please fix up your code indentation so that it makes sense? Are you defining log inside the consolelogging function? If so, you'll need to either make it global with global log or return it from the function and assign it to a variable log on the line where you call the function.

Answer 2

Your main.py doesn't do anything to define the name log in the global namespace. Importing a module can define names in the namespace of that module, but can't put anything in the global namespace.

In your main.py you should add this statement:

from clusterlogging.differentlogging import log

By the way, I that is such a long module name, I would use import as:

import clusterlogging.differentlogging as difflogging
log = difflogging.log

EDIT: I originally recommended this but it won't work:

from difflogging import log  # doesn't work

You might even want to use a really short name like dl:

import clusterlogging.differentlogging as dl
dl.log('whatever')

Since dl is really short, maybe you don't need to get log bound in the global namespace.

Also, you could get every name from a module by using import * but this is not recommended.

from clusterlogging.differentlogging import *  # not recommended

You usually don't want to clutter the global namespace with all the stuff defined in a module. Import just what you need. This is tidier and helps document what you are actually using.

Answer 3

This will return the log array, and you will be able to use the logging function associated.

main.py:

#!/usr/bin/env python

import sys

sys.path.append('CLUSTER')
import clusterlogging.differentlogging
log=clusterlogging.differentlogging.ttylogging()

log.debug("Logging module loaded")
log.info ("It worked")

differentlogging.py :

#!/usr/bin/env python

def ttylogging():
    print "Console Logging loaded"
    import sys
    import logging
    class NullHandler(logging.Handler):
        def emit(self, record):
            pass

    DEFAULTLOGLEVEL=logging.INFO
    log = logging.getLogger(__name__)
    log.addHandler(NullHandler())

    log.setLevel(DEFAULTLOGLEVEL)
    logStreamHandler = logging.StreamHandler(sys.stdout)
    logStreamHandler.setFormatter(logging.Formatter("%(asctime)s %(levelname)5s %(name)s %(lineno)d: %(message)s"))
    log.addHandler(logStreamHandler)

    return log  

def mysqllogging():
    print "mysql logging module here"

def sysloglogging():
    print "rsyslog logging module here"