something randomly made me realize why my second solution didn't work, so i
fixed it. now you have a working persistent deque.
1. if you call somepdequeobject.load(filename) (as opposed to
pdeque.load(filename)), do you want it to return a new object that it loaded
from file, or do you want it to change somepdequeobject to be the object in
the file? i'm not sure which way is canonical.
2. i'm not sure if i actually have to use a temp file and then copy it. i
don't know if pickle.dump as an "atomic commit".
3. cPickle would be faster but i think that means you might end up storing
something in your deque that can't be pickled, like a circular reference,
and dunno what else.
4. can someone tell me if the way i'm using the decorator is sane? i've
never used decorators before. it just seems ridiculous to a) define a lambda
that just throws away the parameter, and b) define a meaningless function to
pass to that lambda.
5. Of course, I am a genius.
from collections import deque
import os, pickle, random
class pdeque(deque):
def __init__(self, filename, initial=None):
if initial is None: initial = []
deque.__init__(self, initial)
self.filename = filename
self.tempfilename = ''.join((random.choice("abcdefghijklmnopqrstuvwxyz")
for x in xrange(10)))+".tmp"
self.save()
def save(self):
pickle.dump(deque(self), open(self.tempfilename,'wb'))
try: os.remove(self.filename)
except: pass
os.rename(self.tempfilename, self.filename)
@classmethod
def load(cls, filename):
return pdeque(filename, pickle.load(open(filename,'rb')))
#todo: change this so that if it's called from an object it loads
#the data into that object?
def makefunc(func):
def func2(instance, *args):
result = func(instance, *args)
instance.save()
return result
return lambda _: func2
for name, func in deque.__dict__.items():
if (not name.startswith("_")) or name in ('__delitem__', '__setitem__'):
@makefunc(func)
def f(): pass
setattr(pdeque, name, f)
"castironpi" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> I'd like a persistent deque, such that the instance operations all
> commit atomicly to file system.
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