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It is now considered a historical accident that e.g. `for` loops and the `iter()` built-in function do not require the iterators they work with to define `__iter__`, only `__next__`.
72 lines
2 KiB
ReStructuredText
72 lines
2 KiB
ReStructuredText
.. highlight:: c
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.. _iterator:
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Iterator Protocol
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=================
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There are two functions specifically for working with iterators.
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.. c:function:: int PyIter_Check(PyObject *o)
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Return non-zero if the object *o* can be safely passed to
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:c:func:`PyIter_Next`, and ``0`` otherwise. This function always succeeds.
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.. c:function:: int PyAIter_Check(PyObject *o)
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Returns non-zero if the object 'obj' provides :class:`AsyncIterator`
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protocols, and ``0`` otherwise. This function always succeeds.
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.. versionadded:: 3.10
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.. c:function:: PyObject* PyIter_Next(PyObject *o)
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Return the next value from the iterator *o*. The object must be an iterator
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according to :c:func:`PyIter_Check` (it is up to the caller to check this).
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If there are no remaining values, returns ``NULL`` with no exception set.
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If an error occurs while retrieving the item, returns ``NULL`` and passes
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along the exception.
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To write a loop which iterates over an iterator, the C code should look
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something like this::
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PyObject *iterator = PyObject_GetIter(obj);
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PyObject *item;
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if (iterator == NULL) {
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/* propagate error */
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}
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while ((item = PyIter_Next(iterator))) {
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/* do something with item */
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...
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/* release reference when done */
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Py_DECREF(item);
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}
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Py_DECREF(iterator);
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if (PyErr_Occurred()) {
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/* propagate error */
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}
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else {
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/* continue doing useful work */
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}
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.. c:type:: PySendResult
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The enum value used to represent different results of :c:func:`PyIter_Send`.
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.. versionadded:: 3.10
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.. c:function:: PySendResult PyIter_Send(PyObject *iter, PyObject *arg, PyObject **presult)
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Sends the *arg* value into the iterator *iter*. Returns:
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- ``PYGEN_RETURN`` if iterator returns. Return value is returned via *presult*.
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- ``PYGEN_NEXT`` if iterator yields. Yielded value is returned via *presult*.
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- ``PYGEN_ERROR`` if iterator has raised and exception. *presult* is set to ``NULL``.
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.. versionadded:: 3.10
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