Re: Understanding other people's code
Literally any idea will help, pen and paper, printing off all the code and doing some sort of highlighting session - anything! I keep reading bits of code and thinking well where the hell has that been defined and what does it mean to find it was inherited from 3 modules up the chain. I really need to get a handle on how exactly all this slots together! Any techniques,tricks or methodologies that people find useful would be much appreciated. I'd highly recommend Eclipse with PyDev, unless you have some strong reason not to. That's what I use, and it saves pretty much all of those what's this thing? problems, as well as lots of others... DC -- http://mail.python.org/mailman/listinfo/python-list
Re: Functional vs. Object oriented API
Roy Smith r...@panix.com As part of our initial interview screen, we give applicants some small coding problems to do. One of the things we see a lot is what you could call Java code smell. This is our clue that the person is really a Java hacker at heart who just dabbles in Python but isn't really fluent. ... It's not just LongVerboseFunctionNamesInCamelCase(). Nor is it code that looks like somebody bought the Gang of Four patterns book and is trying to get their money's worth out of the investment. The real dead giveaway is when they write classes which contain a single static method and nothing else. I may have some lingering Java smell myself, although I've been working mostly in Python lately, but my reaction here is that's really I don't know BASIC smell or something; a class that contains a single static method and nothing else isn't wonderful Java design style either. That being said, I've noticed in my own coding, it's far more often that I start out writing some functions and later regret not having initially made it a class, than the other way around. That's as true in my C++ code as it is in my Python. Definitely. Once you start having state (i.e. data) and behavior (i.e. functions) in the same thought, then you need a class. If you find yourself passing the same bunch of variables around to multiple functions, that's a hint that maybe there's a class struggling to be written. And I think equally to the point, even if you have only data, or only functions, right now, if the thing in question has that thing-like feel to it :) you will probably find yourself with both before you're done, so you might as well make it a class now... DC -- http://mail.python.org/mailman/listinfo/python-list
Re: Cannot run a single MySQLdb execute....
Νίκος Γκρ33κ nikos.gr...@gmail.com : What paramstyle are you using? Yes it is Chris, but i'am not sure what exactly are you asking me. Please if you cna pout it even simper for me, thank you. For instance: import MySQLdb MySQLdb.paramstyle 'format' FWIW and HTH, DC -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a TimedRotatingFileHandler not to put two dates in the same file?
d...@davea.name On 10/23/2012 11:23 AM, David M Chess wrote: We have a TimedRotatingFileHandler with when='midnight' You give us no clue what's in this class, or how it comes up with the filenames used. Sorry if I was unclear. This isn't my own subclass of TimedRotatingFileHandler or anything, this is the bog-standard logging.handlers.TimedRotatingFileHandler I'm talking about. So all clues about what's in the class, and how it comes up with the filenames used, is available at http://docs.python.org/library/logging.handlers.html#timedrotatingfilehandler :) The specific Python version involved here is Python 2.6.6 (r266:84297, Aug 24 2010, 18:46:32), to the extent that that matters... This works great, splitting the log information across files by date, as long as the process is actually up at midnight. But now the users have noticed that if the process isn't up at midnight, they can end up with lines from two (or I guess potentially more) dates in the same log file. Is there some way to fix this, either with cleverer arguments into the TimedRotatingFileHandler, or by some plausible subclassing of it or its superclass? Tx, DC http://mail.python.org/mailman/listinfo/python-list
Re: Getting a TimedRotatingFileHandler not to put two dates in the same file?
w...@mac.com Something like: Does a log file exist? - No - First run; create log file continue | Yes | Read backwards looking for date change, copy lines after change to new file, delete from old file. Yep, I'm concluding that also. It just wasn't clear to me from the documentation whether or not the existing TimedRotatingFileHandler had any at startup, see if we missed any rollovers, and do them now if so function, or if there was some known variant that does. The answer, apparently, being nope. :) Shouldn't be that hard to write, so that's probably what we'll do. DC --- -- http://mail.python.org/mailman/listinfo/python-list
A lock that prioritizes acquire()s?
Okay, next silly question. :)
We have a very simple multi-threaded system where a request comes in,
starts running in a thread, and then (zero, one, or two times per request)
gets to a serialization point, where the code does:
with lock:
do_critical_section_stuff_that_might_take_awhile()
and then continues.
Which is almost the same as:
lock.acquire()
try:
do_critical_section_stuff_that_might_take_awhile()
finally:
lock.release()
Now we discover that It Would Be Nice if some requests got priority over
others, as in something like:
lock.acquire(importance=request.importance)
try:
do_critical_section_stuff_that_might_take_awhile()
finally:
lock.release()
and when lock.release() occurs, the next thread that gets to run is one of
the most important ones currently waiting in acquire() (that's the
exciting new thing).
Other requirements are that the code to do this be as simple as possible,
and that it not mess anything else up. :)
My first thought was something like a new lock-ish class that would do
roughly:
class PriorityLock(object):
def __init__(self):
self._lock = threading.Lock()
self._waiter_map = {} # maps TIDs to importance
def acquire(self,importance=0):
this_thread = threading.currentThread()
self._waiter_map[this_thread] = importance # I want in
while True:
self._lock.acquire()
if ( max( self._waiter_map.values())=importance ): # we win
del self._waiter_map[this_thread] # not waiting anymore
return # return with lock acquired
self._lock.release() # We are not most impt: release/retry
def release(self):
self._lock.release()
(Hope the mail doesn't garble that too badly.)
Basically the acquire() method just immediately releases and tries again
if it finds that someone more important is waiting.
I think this is semantically correct, as long as the underlying lock
implementation doesn't have starvation issues, and it's nice and simple,
but on the other hand it looks eyerollingly inefficient.
Seeking any thoughts on other/better ways to do this, or whether the
inefficiency will be too eyerolling if we get say one request per second
with an average service time a bit under a second but maximum service time
well over a second, and most of them are importance zero, but every (many)
seconds there will be one or two with higher importance.
Tx,
DC
---
--
http://mail.python.org/mailman/listinfo/python-list
Re: A lock that prioritizes acquire()s?
Lovely, thanks for the ideas! I remember considering having release() pick the next thread to notify, where all the waiters were sitting on separate Conditions or whatever; not sure why I didn't pursue it to the end. Probably distracted by something shiny; or insufficient brainpower. :) DC -- -- http://mail.python.org/mailman/listinfo/python-list
Getting a TimedRotatingFileHandler not to put two dates in the same file?
We have a TimedRotatingFileHandler with when='midnight'. This works great, splitting the log information across files by date, as long as the process is actually up at midnight. But now the users have noticed that if the process isn't up at midnight, they can end up with lines from two (or I guess potentially more) dates in the same log file. Is there some way to fix this, either with cleverer arguments into the TimedRotatingFileHandler, or by some plausible subclassing of it or its superclass? Or am I misinterpreting the symptoms somehow? Tx much! DC -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with ThreadingTCPServer Handler
jorge jaoro...@estudiantes.uci.cu I'm programming a server that most send a message to each client connected to it and nothing else. this is obviously a base of what i want to do. the thing is, I made a class wich contains the Handler class for the ThreadingTCPServer and starts the server but i don't know how can i access the message variable contained in the class from the Handler since I have not to instance the Handler by myself. The information about the request is in attributes of the Handler object. From the socketserver docs ( http://docs.python.org/library/socketserver.html ): RequestHandler.handle() This function must do all the work required to service a request. The default implementation does nothing. Several instance attributes are available to it; the request is available as self.request; the client address asself.client_address; and the server instance as self.server, in case it needs access to per-server information. If that's what you meant by the message variable contained in the class. If, on the other hand, you meant that you want to pass some specific data into the handler about what it's supposed to be doing, I've generally stashed that in the server, since the handler can see the server via self.server. DC -- http://mail.python.org/mailman/listinfo/python-list
Re: Py3.3 unicode literal and input()
If you (the programmer) want a function that asks the user to enter a literal at the input prompt, you'll have to write a post-processing for it, which looks for prefixes, for quotes, for backslashes, etc., and encodes the result. There very well may be such a decoder in the Python library, but input does nothing of the kind. As it says at the end of eval() (which you definitely don't want to use here due to side effects): See ast.literal_eval() for a function that can safely evaluate strings with expressions containing only literals. DC -- http://mail.python.org/mailman/listinfo/python-list
bus errors when the network interface is reset?
We have a system running Python 2.6.6 under RHEL 6.1. A bunch of processes spend most of their time sitting in a BaseHTTPServer.HTTPServer waiting for requests. Last night an update pushed out via xcat whimsically restarted all of the network interfaces, and at least some of our processes died with bus errors (i.e. no errors or exceptions reflected up to the Python level, just a crash). This is just my initial looking into this. Seeking opinions of the form, say: Yeah, that happens, don't reset the network interfaces. Yeah, that happens, and you can prevent the crash by doing X in your OS. Yeah, that happens, and you can prevent the crash by doing X in your Python code. That wouldn't happen if you upgraded S to version V. That sounds like a new bug and/or more information is needed; please provide copious details including at least X, Y, and Z. Any thoughts or advice greatly appreciated. DC David M. Chess IBM Watson Research Center -- http://mail.python.org/mailman/listinfo/python-list
