Using iterators to write in the structure being iterated through?

[Pierre Thibault]

Hello!

I am currently trying to port a C++ code to python, and I think I am stuck
because of the very different behavior of STL iterators vs python
iterators. What I need to do is a simple arithmetic operations on objects
I don't know. In C++, the method doing that was a template, and all that
was required is that the template class has an iterator conforming to the
STL forward iterator definition. Then, the class would look like:

template <class H>
class MyClass
{
public:

	MyClass(H& o1, H& o2) : object1(o1), object2(o2) {}

	void compute();

private:
	H& object1;
	H& object2;

};

template <class H>
void MyClass::compute()
{
	typedef typename H::iterator I;

	I o1_begin = object1.begin();
	I o2_begin = object2.begin();
        I o1_end = object1.end();

	for(I io1 = o1_begin, io2 = o2_begin; io1 != o1_end; ++io1, ++io2)
 	{
		// Do something with *io1 and *io2, for instance:
		// *io1 += *io2;
	}
}

This is all nice: any object having a forward iterator works in there.

Then I discovered python and wanted to use all its goodies. I thought it
would be easy to do the same thing but I can't: the iterator mechanism is
read-only, right? So it does no make sense to write:

io1 = iter(object1)
io2 = iter(object2)

try:
  while 1:
    io1.next() += io2.next()
except StopIteration:
  pass

That won't work:
SyntaxError: can't assign to function call

Here is my question: how could I do that and retain enough generallity?

Thanks!

Pierre