On 14Oct2012 18:32, Ian Kelly <ian.g.ke...@gmail.com> wrote: | On Sun, Oct 14, 2012 at 3:54 PM, Cameron Simpson <c...@zip.com.au> wrote: | > | You assign to it, but there's no nonlocal declaration, so Python thinks | > | it's a local var, hence your error. | > | > But 'unset_object' is in locals(). Why one and not the other? | > Obviously there's something about closures here I'm missing. | | 'unset_object' is in locals because it's a free variable and those are | included in locals(), and it has a value. | | 'attr_name' is not in locals because while it's a local variable, it | has not been assigned to yet. It has no value and an attempt to | reference it at that point would result in an UnboundLocalError.
Can you elaborate a bit on that? The only place in my code that unset_object is set is as a default parameter in make_file_property (snippet): def make_file_property(attr_name=None, unset_object=None, poll_rate=1): print >>sys.stderr, "make_file_property(attr_name=%r, unset_object=%r, poll_rate=%r): locals()=%r" % (attr_name, unset_object, poll_rate,locals()) def made_file_property(func): print >>sys.stderr, "made_file_property(func=%r): locals()=%r" % (func, locals()) if attr_name is None: attr_name = '_' + func.__name__ and attr_name is set there also. Is attr_name omitted from locals() in made_file_property _because_ I have an assignment statement? If that's the case, should I be doing this (using distinct names for the closure variable and the function local variable): def make_file_property(attr_name=None, unset_object=None, poll_rate=1): print >>sys.stderr, "make_file_property(attr_name=%r, unset_object=%r, poll_rate=%r): locals()=%r" % (attr_name, unset_object, poll_rate,locals()) def made_file_property(func): print >>sys.stderr, "made_file_property(func=%r): locals()=%r" % (func, locals()) if attr_name is None: my_attr_name = '_' + func.__name__ else: my_attr_name = attr_name lock_name = my_attr_name + '_lock' def getprop(self): with getattr(self, lock_name): pass return getattr(self, my_attr_name, unset_object) i.e. deliberately _not_ assigning to attr_name as as to _avoid_ masking the outer attr_name from the inner locals()? BTW, doing that works. Is that The True Path for this situation? If so, I think I now understand what's going on: Python has inspected the inner function and not placed the outer 'attr_name' into locals() _because_ the inner function seems to have its own local attr_name in use, which should not be pre-tromped. -- Cameron Simpson <c...@zip.com.au> Nothing is so smiple that it can't get screwed up. -- http://mail.python.org/mailman/listinfo/python-list