Python provides two general-purpose iterator objects. The first, a sequence iterator, works with an arbitrary sequence supporting the __getitem__() method. The second works with a callable object and a sentinel value, calling the callable for each item in the sequence, and ending the iteration when the sentinel value is returned.
PyTypeObject PySeqIter_Type Type object for iterator objects returned by PySeqIter_New() and the one-argument form of the iter() built-in function for built-in sequence types.
int PySeqIter_Check(PyObject *op) Return true if the type of op is PySeqIter_Type. This function always succeeds.
PyObject *PySeqIter_New(PyObject *seq) Return an iterator that works with a general sequence object, seq. The iteration ends when the sequence raises IndexError for the subscripting operation.
PyTypeObject PyCallIter_Type Type object for iterator objects returned by PyCallIter_New() and the two-argument form of the iter() built-in function.
int PyCallIter_Check(PyObject *op) Return true if the type of op is PyCallIter_Type. This function always succeeds.
PyObject *PyCallIter_New(PyObject *callable, PyObject *sentinel) Return a new iterator. The first parameter, callable, can be any Python callable object that can be called with no parameters; each call to it should return the next item in the iteration. When callable returns a value equal to sentinel, the iteration will be terminated.
PyTypeObject PyRange_Type The type object for range objects.
int PyRange_Check(PyObject *o) Return true if the object o is an instance of a range object. This function always succeeds.
These are built-in iteration types that are included in Python’s C API, but provide no additional functions. They are here for completeness.
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PyTypeObject PyByteArrayIter_Type PyTypeObject PyBytesIter_Type PyTypeObject PyListIter_Type PyTypeObject PyListRevIter_Type PyTypeObject PySetIter_Type PyTypeObject PyTupleIter_Type PyTypeObject PyRangeIter_Type PyTypeObject PyLongRangeIter_Type PyTypeObject PyDictIterKey_Type PyTypeObject PyDictRevIterKey_Type PyTypeObject PyDictIterValue_Type PyTypeObject PyDictRevIterValue_Type PyTypeObject PyDictIterItem_Type PyTypeObject PyDictRevIterItem_Type PyTypeObject PyODictIter_Type Type objects for iterators of various built-in objects.
Do not create instances of these directly; prefer calling PyObject_GetIter() instead.
Note that there is no guarantee that a given built-in type uses a given iterator type. For example, iterating over range will use one of two iterator types depending on the size of the range. Other types may start using a similar scheme in the future, without warning.
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https://docs.python.org/3.14/c-api/iterator.html