But you didn't do an assignment, you did an append. Append modifies the
object, which is referenced by both parent_struct_sig and
this_cdata["struct-sig"]
If you're sure you want a *copy* of the list before the modifications,
you might do something like
parent_struct_sig = \
self.__class_data[this_class]["struct-sig"][:]
If the items in the list might be modified as well, then you might have
to do something like copy.deepcopy()
Edd Barrett wrote:
Hi there,
My first post here, so hello :)
Just a little background, I am writing my dissertation, which is a JIT
compiler based upon LLVM and it's python bindings, along with the
aperiot LL(1) parser.
I have some code here, which is not behaving as I would expect. Could
someone enlighten me as to why this is so:
---8<---
def __classdef_integer(self):
"""
class definition for a integer object.
"""
this_class = "Integer"
# metadata inherited
self.__class_data[this_class] = \
self.__class_data["Object"]
# cache parent struct sig for later (when casting ptrs)
parent_struct_sig = \
self.__class_data[this_class]["struct-sig"]
this_cdata = self.__class_data[this_class]
#this_cdata["membernames"].append("value")
#this_cdata["type-sym"] = 1
#this_cdata["parent-class"] = "Object"
#vtab = self.__construct_vtable(this_class)
#self.__ir_add_typesym(this_class, vtab)
print "parent::::"
print parent_struct_sig
this_cdata["struct-sig"].append(self.__int_t)
print "new::::"
print parent_struct_sig
sys.exit(1)
---8<---
Notice how I am caching the old value of 'parent_struct_sig' before I
manipulate it.
Produces the following output:
---8<---
parent::::
[<llvm.core.PointerType object at 0x7fcdfdac>]
new::::
[<llvm.core.PointerType object at 0x7fcdfdac>, <llvm.core.IntegerType
object at 0x8231520c>]
---8<---
My question is: why has 'parent_struct_sig' changed? I was under the
impression the assignment operator copies, not references.
Sorry if the answer is blindingly obvious. I am somewhat jaded from
working on this every day :P
Heres my python environment:
---8<---
Python 2.6.1 (r261:67515, Dec 27 2008, 16:56:14)
[GCC 4.2.0 20070307 (prerelease)] on openbsd4
Type "help", "copyright", "credits" or "license" for more information.
---8<---
Thanks
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