On 09/03/2013 09:07 AM, Gildor Oronar wrote:
What would you choose? Do you put logging routine into caller or callee? My
intuitive answer is "callee does the
logging, because that's where action takes place", like this:
class Account():
def transaction(self, amount, target):
logging.info("Start transaction of %s to %s" % (amount, target))
...
So far so good, but we grew up to have 10 different account classes:
class AbsctractAccount():
class CreditAccount(AbstractAccount):
def transaction(self, amount, target):
logging.info("Start transaction of %s to %s" % (amount, target))
...
class DebitAccount(AbstractAccount):
def transaction(self, amount, target):
logging.info("Start transaction of %s to %s" % (amount, target))
...
class SomeOtherAccount(...)
....
Then letting the callee do the logging is also tedious now.
What is the best practise here?
If, for the convenience, we define transaction function in AbstractAccount to
just do the logging, and change inherited
classes, like this:
class AbsctractAccount():
def transaction(self, amount, target):
logging.info("Start transaction of %s to %s" % (amount, target))
class DebitAccount(AbstractAccount):
def transaction(self, amount, target):
super().transaction(amount,target)
....
In this instance you're not really gaining anything by using inheritance: before you had one line for logging, after you
have one line to call super(); in either case if you forget the one line you don't get a log entry.
I would say it is not really the caller's or the callee's job to do the logging, even though it should be done. What
would be really handy is a function that sat in between the caller and callee that logged for you -- you know, a decorator:
# not tested, but hopefully you get the idea
def log(func):
def wrapper(*args, **kwds):
text = []
if args:
text.append(str(args))
if kwds:
text.append(str(kwds))
text = ', '.join(text)
if text:
logging.info("%s called with %s" % (func.__name__, text)
else:
logging.info("%s called" % func.__name__)
return func(*args, **kwds)
return wrapper
Then you can say:
class WhateverAccount:
@log
def transaction(self, amount, target):
...
True, you still one line, but moves the logging concern outside the function, where it doesn't really belong. It also
makes it really easy to see if a function will be logged or not.
--
~Ethan~
--
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