Iterators phase 1. This comprises: new slot tp_iter in type object, plus new flag Py_TPFLAGS_HAVE_ITER new C API PyObject_GetIter(), calls tp_iter new builtin iter(), with two forms: iter(obj), and iter(function, sentinel) new internal object types iterobject and calliterobject new exception StopIteration new opcodes for "for" loops, GET_ITER and FOR_ITER (also supported by dis.py) new magic number for .pyc files new special method for instances: __iter__() returns an iterator iteration over dictionaries: "for x in dict" iterates over the keys iteration over files: "for x in file" iterates over lines TODO: documentation test suite decide whether to use a different way to spell iter(function, sentinal) decide whether "for key in dict" is a good idea use iterators in map/filter/reduce, min/max, and elsewhere (in/not in?) speed tuning (make next() a slot tp_next???)