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documentation improvements
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Wenzel Jakob
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978e376e57
@ -373,10 +373,10 @@ Passing STL data structures
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===========================
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When including the additional header file :file:`pybind11/stl.h`, conversions
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between ``std::vector<>``, ``std::set<>``, and ``std::map<>`` and the Python
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``list``, ``set`` and ``dict`` data structures are automatically enabled. The
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types ``std::pair<>`` and ``std::tuple<>`` are already supported out of the box
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with just the core :file:`pybind11/pybind11.h` header.
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between ``std::vector<>``, ``std::list<>``, ``std::set<>``, and ``std::map<>``
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and the Python ``list``, ``set`` and ``dict`` data structures are automatically
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enabled. The types ``std::pair<>`` and ``std::tuple<>`` are already supported
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out of the box with just the core :file:`pybind11/pybind11.h` header.
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.. note::
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@ -457,7 +457,7 @@ See below for an example that uses the
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py::class_<Example>(m, "Example")
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.def(py::init<>())
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.def("get_internal", &Example::get_internal, "Return the internal data", py::return_value_policy::reference_internal)
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.def("get_internal", &Example::get_internal, "Return the internal data", py::return_value_policy::reference_internal);
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return m.ptr();
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}
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@ -705,23 +705,35 @@ automatically converted into a Python ``Exception``. pybind11 defines multiple
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special exception classes that will map to different types of Python
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exceptions:
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+----------------------------+------------------------------+
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| C++ exception type | Python exception type |
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+============================+==============================+
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| :class:`std::exception` | ``Exception`` |
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+----------------------------+------------------------------+
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| :class:`stop_iteration` | ``StopIteration`` (used to |
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| | implement custom iterators) |
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+----------------------------+------------------------------+
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| :class:`index_error` | ``IndexError`` (used to |
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| | indicate out of bounds |
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| | accesses in ``__getitem__``, |
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| | ``__setitem__``, etc.) |
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+----------------------------+------------------------------+
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| :class:`error_already_set` | Indicates that the Python |
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| | exception flag has already |
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| | been initialized. |
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+----------------------------+------------------------------+
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+--------------------------------------+------------------------------+
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| C++ exception type | Python exception type |
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+======================================+==============================+
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| :class:`std::exception` | ``RuntimeError`` |
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+--------------------------------------+------------------------------+
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| :class:`std::bad_alloc` | ``MemoryError`` |
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+--------------------------------------+------------------------------+
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| :class:`std::domain_error` | ``ValueError`` |
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+--------------------------------------+------------------------------+
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| :class:`std::invalid_argument` | ``ValueError`` |
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+--------------------------------------+------------------------------+
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| :class:`std::length_error` | ``ValueError`` |
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+--------------------------------------+------------------------------+
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| :class:`std::out_of_range` | ``ValueError`` |
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+--------------------------------------+------------------------------+
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| :class:`std::range_error` | ``ValueError`` |
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+--------------------------------------+------------------------------+
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| :class:`pybind11::stop_iteration` | ``StopIteration`` (used to |
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| | implement custom iterators) |
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+--------------------------------------+------------------------------+
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| :class:`pybind11::index_error` | ``IndexError`` (used to |
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| | indicate out of bounds |
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| | accesses in ``__getitem__``, |
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| | ``__setitem__``, etc.) |
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+--------------------------------------+------------------------------+
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| :class:`pybind11::error_already_set` | Indicates that the Python |
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| | exception flag has already |
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| | been initialized |
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+--------------------------------------+------------------------------+
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When a Python function invoked from C++ throws an exception, it is converted
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into a C++ exception of type :class:`error_already_set` whose string payload
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@ -735,9 +747,9 @@ Buffer protocol
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===============
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Python supports an extremely general and convenient approach for exchanging
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data between plugin libraries. Types can expose a buffer view which provides
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fast direct access to the raw internal representation. Suppose we want to bind
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the following simplistic Matrix class:
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data between plugin libraries. Types can expose a buffer view [#f1]_,
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which provides fast direct access to the raw internal representation. Suppose
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we want to bind the following simplistic Matrix class:
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.. code-block:: cpp
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@ -829,12 +841,14 @@ objects (e.g. a NumPy matrix).
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The file :file:`example/example7.cpp` contains a complete example that
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demonstrates using the buffer protocol with pybind11 in more detail.
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.. [#f1] https://docs.python.org/3/c-api/buffer.html
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NumPy support
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=============
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By exchanging ``py::buffer`` with ``py::array`` in the above snippet, we can
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restrict the function so that it only accepts NumPy arrays (rather than any
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type of Python object satisfying the buffer object protocol).
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type of Python object satisfying the buffer protocol).
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In many situations, we want to define a function which only accepts a NumPy
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array of a certain data type. This is possible via the ``py::array_t<T>``
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@ -846,8 +860,9 @@ dense array of doubles in C-style ordering.
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void f(py::array_t<double> array);
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When it is invoked with a different type (e.g. an integer), the binding code
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will attempt to cast the input into a NumPy array of the requested type.
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Note that this feature requires the ``pybind11/numpy.h`` header to be included.
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will attempt to cast the input into a NumPy array of the requested type. Note
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that this feature requires the :file:``pybind11/numpy.h`` header to be
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included.
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Vectorizing functions
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=====================
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@ -867,7 +882,10 @@ After including the ``pybind11/numpy.h`` header, this is extremely simple:
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m.def("vectorized_func", py::vectorize(my_func));
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Invoking the function like below causes 4 calls to be made to ``my_func`` with
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each of the the array elements. The result is returned as a NumPy array of type
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each of the the array elements. The significant advantage of this compared to
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solutions like ``numpy.vectorize()`` is that the loop over the elements runs
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entirely on the C++ side and can be crunched down into a tight, optimized loop
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by the compiler. The result is returned as a NumPy array of type
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``numpy.dtype.float64``.
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.. code-block:: python
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@ -1085,8 +1103,6 @@ lookup of the corresponding Python type. However, this also requires invoking
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the ``import`` function once to ensure that the pybind11 binding code of the
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module ``basic`` has been executed.
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Naturally, both methods will fail when there are cyclic dependencies.
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.. code-block:: cpp
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py::module::import("basic");
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@ -1095,6 +1111,8 @@ Naturally, both methods will fail when there are cyclic dependencies.
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.def(py::init<const std::string &>())
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.def("bark", &Dog::bark);
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Naturally, both methods will fail when there are cyclic dependencies.
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Treating STL data structures as opaque objects
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==============================================
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@ -1104,9 +1122,9 @@ linked lists, hash tables, etc. This even works in a recursive manner, for
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instance to deal with lists of hash maps of pairs of elementary and custom
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types, etc.
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The fundamental limitation of this approach is the internal conversion between
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Python and C++ types involves a copy operation that prevents pass-by-reference
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semantics. What does this mean?
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A fundamental limitation of this approach is that the internal conversion
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between Python and C++ types involves a copy operation that prevents
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pass-by-reference semantics. What does this mean?
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Suppose we bind the following function
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