En Thu, 31 Jan 2008 01:57:41 -0200, Dan Upton <[EMAIL PROTECTED]> escribió:
> Or: How to write Python like a Python programmer, not a Java > programmer. This will be a little long-winded... > > So I just recently started picking up Python, mostly learning the new > bits I need via Google and otherwise cobbling together the functions > I've already written. It occurred to me though that one of my > programs was still probably written very much like I would in Java > (part of the reason I'm picking up Python is I'm tired of my coworkers > making fun of me for writing parsing/reformatting programs in Java). Maybe you've already read this, but I'll post the links anyway: http://dirtsimple.org/2004/12/python-is-not-java.html http://dirtsimple.org/2004/12/java-is-not-python-either.html > Anyway, basically here's the problem I have: > > -Fork off n copies of a program, where n is a command line parameter, > and save their PIDs. The way I've been accomplishing this is > basically: > > processes=[] > for i in range(numProcs): > pid=os.fork() > if pid == 0: > # do the forking > else: > processes.append(pid) Looks fine to me. > -Every so much time (say, every second), I want to ask the OS > something about that process from under /proc/pid (this is on Linux), > including what core it's on. > while 1: > for i in processes: > file = open("/proc/"+str(i)+"/stat") (I hope there is a time.sleep(1) after processing that) - don't use file as a variable name, you're shadowing the builtin file type. - "i" is very much overloaded as a variable name everywhere... I'd use pid instead - string interpolation looks better (and is faster, but that's not so relevant here) for pid in processes: statfile = open("/proc/%d/stat" % pid) >> From that, one of the pieces of data I'll get is which core it's > running on, which then will prompt me to open another file. > Ultimately, I want to have n files, that are a bunch of lines: > corenum data1 data2 ... > corenum data1 data2 ... > ... > > and so on. The way I was going to approach it was to every time > through the loop, read the data for one of the processes, open its > file, write out to it, and close it, then do the same for the next > process, and so on. Really though I don't need to be able to look at > the data until the processes are finished, and it would be less I/O, > at the expense of memory, to just save all of the lists of data as I > go along and then dump them out to disk at the end of the Python > program's execution. I feel like Python's lists or dictionaries > should be useful here, but I'm not really sure how to apply them, > particularly in a "Python-like" way. > > For anybody who made it all the way through that description ;) any > suggestions? The simplest solution would be to use a tuple to store a row of data. You know (implicitely) what every element contains: the first item is "corenum", the second item is "data1", the third item is "data2" and so on... (based on your example above). Collect those tuples (rows) into a list (one list per process), and collect all lists into a dictionary indexed by pid. That is, at the beginning, create an empty dictionary: info = {} After each forking, at the same time you save the pid, create the empty list: info[pid] = [] After you read and process the /proc file to obtain what you want, apend a new element to that list: info[pid].append((corenum, data1, data2, ...)) (notice the double parenthesis) At the end, write all that info on disk. The csv module looks like a good candidate: import csv for pid in processes: writer = csv.writer(open("process-%d.csv" % pid, "wb")) writer.writerows(info[pid]) That's all -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
