Hi,
I'm trying to write a decorator which allows one to produce simple
coroutines by just writing a function as a generator expression which
re-receives it's arguments as a tuple from each yield. For example:
@coroutine
def nextn(n=1):
values = []
for i in itertools.count():
while n <= 0:
(n,) = (yield values)
values = []
values.append(i)
n = n - 1
print nextn() # => [0]
print nextn(3) # => [1, 2, 3]
print nextn(n=2) # => [4, 5]
print nextn() # => [6]
I've got this working, but have two questions. First, is there a better
way to generically transform function arguments into a tuple than I'm
doing now? That way being with this pretty hideous chunk of code:
class ArgPacker(object):
def __init__(self, function):
args, varargs, varkw, defaults = inspect.getargspec(function)
self.args = args or []
self.varargs = (varargs is not None) and 1 or 0
self.varkw = (varkw is not None) and 1 or 0
self.nargs = len(self.args) + self.varargs + self.varkw
defaults = defaults or []
defargs = self.args[len(self.args) - len(defaults):]
self.defaults = dict([(k, v) for k, v in izip(defargs, defaults)])
def pack(self, *args, **kwargs):
args = list(args)
result = [None] * self.nargs
for i, arg in izip(xrange(len(self.args)), self.args):
if args:
result[i] = args.pop(0)
elif arg in kwargs:
result[i] = kwargs[arg]
del kwargs[arg]
elif arg in self.defaults:
result[i] = self.defaults[arg]
else:
return None
if self.varargs:
result[len(self.args)] = args
elif args:
return None
if self.varkw:
result[-1] = kwargs
elif kwargs:
return None
return tuple(result)
I also tried a version using exec, which was much tighter, but used
exec.
Second, am I trying to hammer a nail with a glass bottle here? The
ugliness of the ArgPacker class makes me suspect that I should perhaps
just manually create and track a generator when I need a function with
generator-like properties.
Thanks!
-Marshall
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