iCE40/yosys - clone of https://github.com/YosysHQ/yosys

about summary refs log tree commit diff stats

diff options

Diffstat (limited to 'examples/python-api')

0 files changed, 0 insertions, 0 deletions

>30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251

Python types
############

.. _wrappers:

Available wrappers
==================

All major Python types are available as thin C++ wrapper classes. These
can also be used as function parameters -- see :ref:`python_objects_as_args`.

Available types include :class:`handle`, :class:`object`, :class:`bool_`,
:class:`int_`, :class:`float_`, :class:`str`, :class:`bytes`, :class:`tuple`,
:class:`list`, :class:`dict`, :class:`slice`, :class:`none`, :class:`capsule`,
:class:`iterable`, :class:`iterator`, :class:`function`, :class:`buffer`,
:class:`array`, and :class:`array_t`.

.. warning::

    Be sure to review the :ref:`pytypes_gotchas` before using this heavily in
    your C++ API.

.. _casting_back_and_forth:

Casting back and forth
======================

In this kind of mixed code, it is often necessary to convert arbitrary C++
types to Python, which can be done using :func:`py::cast`:

.. code-block:: cpp

    MyClass *cls = ..;
    py::object obj = py::cast(cls);

The reverse direction uses the following syntax:

.. code-block:: cpp

    py::object obj = ...;
    MyClass *cls = obj.cast<MyClass *>();

When conversion fails, both directions throw the exception :class:`cast_error`.

.. _python_libs:

Accessing Python libraries from C++
===================================

It is also possible to import objects defined in the Python standard
library or available in the current Python environment (``sys.path``) and work
with these in C++.

This example obtains a reference to the Python ``Decimal`` class.

.. code-block:: cpp

    // Equivalent to "from decimal import Decimal"
    py::object Decimal = py::module_::import("decimal").attr("Decimal");

.. code-block:: cpp

    // Try to import scipy
    py::object scipy = py::module_::import("scipy");
    return scipy.attr("__version__");


.. _calling_python_functions:

Calling Python functions
========================

It is also possible to call Python classes, functions and methods
via ``operator()``.

.. code-block:: cpp

    // Construct a Python object of class Decimal
    py::object pi = Decimal("3.14159");

.. code-block:: cpp

    // Use Python to make our directories
    py::object os = py::module_::import("os");
    py::object makedirs = os.attr("makedirs");
    makedirs("/tmp/path/to/somewhere");

One can convert the result obtained from Python to a pure C++ version
if a ``py::class_`` or type conversion is defined.

.. code-block:: cpp

    py::function f = <...>;
    py::object result_py = f(1234, "hello", some_instance);
    MyClass &result = result_py.cast<MyClass>();

.. _calling_python_methods:

Calling Python methods
========================

To call an object's method, one can again use ``.attr`` to obtain access to the
Python method.

.. code-block:: cpp

    // Calculate e^π in decimal
    py::object exp_pi = pi.attr("exp")();
    py::print(py::str(exp_pi));

In the example above ``pi.attr("exp")`` is a *bound method*: it will always call
the method for that same instance of the class. Alternately one can create an
*unbound method* via the Python class (instead of instance) and pass the ``self``
object explicitly, followed by other arguments.

.. code-block:: cpp

    py::object decimal_exp = Decimal.attr("exp");

    // Compute the e^n for n=0..4
    for (int n = 0; n < 5; n++) {
        py::print(decimal_exp(Decimal(n));
    }

Keyword arguments
=================

Keyword arguments are also supported. In Python, there is the usual call syntax:

.. code-block:: python


context:
space:
mode: