2 pybind11/embed.h: Support for embedding the interpreter
4 Copyright (c) 2017 Wenzel Jakob <wenzel.jakob@epfl.ch>
6 All rights reserved. Use of this source code is governed by a
7 BSD-style license that can be found in the LICENSE file.
15 #if defined(PYPY_VERSION)
16 # error Embedding the interpreter is not supported with PyPy
19 #if PY_MAJOR_VERSION >= 3
20 # define PYBIND11_EMBEDDED_MODULE_IMPL(name) \
21 extern "C" PyObject *pybind11_init_impl_##name() { \
22 return pybind11_init_wrapper_##name(); \
25 # define PYBIND11_EMBEDDED_MODULE_IMPL(name) \
26 extern "C" void pybind11_init_impl_##name() { \
27 pybind11_init_wrapper_##name(); \
32 Add a new module to the table of builtins for the interpreter. Must be
33 defined in global scope. The first macro parameter is the name of the
34 module (without quotes). The second parameter is the variable which will
35 be used as the interface to add functions and classes to the module.
39 PYBIND11_EMBEDDED_MODULE(example, m) {
40 // ... initialize functions and classes here
42 return "Hello, World!";
46 #define PYBIND11_EMBEDDED_MODULE(name, variable) \
47 static void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &); \
48 static PyObject PYBIND11_CONCAT(*pybind11_init_wrapper_, name)() { \
49 auto m = pybind11::module(PYBIND11_TOSTRING(name)); \
51 PYBIND11_CONCAT(pybind11_init_, name)(m); \
53 } catch (pybind11::error_already_set &e) { \
54 PyErr_SetString(PyExc_ImportError, e.what()); \
56 } catch (const std::exception &e) { \
57 PyErr_SetString(PyExc_ImportError, e.what()); \
61 PYBIND11_EMBEDDED_MODULE_IMPL(name) \
62 pybind11::detail::embedded_module name(PYBIND11_TOSTRING(name), \
63 PYBIND11_CONCAT(pybind11_init_impl_, name)); \
64 void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &variable)
67 NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
68 NAMESPACE_BEGIN(detail)
70 /// Python 2.7/3.x compatible version of `PyImport_AppendInittab` and error checks.
71 struct embedded_module {
72 #if PY_MAJOR_VERSION >= 3
73 using init_t = PyObject *(*)();
75 using init_t = void (*)();
77 embedded_module(const char *name, init_t init) {
78 if (Py_IsInitialized())
79 pybind11_fail("Can't add new modules after the interpreter has been initialized");
81 auto result = PyImport_AppendInittab(name, init);
83 pybind11_fail("Insufficient memory to add a new module");
90 Initialize the Python interpreter. No other pybind11 or CPython API functions can be
91 called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
92 optional parameter can be used to skip the registration of signal handlers (see the
93 `Python documentation`_ for details). Calling this function again after the interpreter
94 has already been initialized is a fatal error.
96 If initializing the Python interpreter fails, then the program is terminated. (This
97 is controlled by the CPython runtime and is an exception to pybind11's normal behavior
98 of throwing exceptions on errors.)
100 .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
102 inline void initialize_interpreter(bool init_signal_handlers = true) {
103 if (Py_IsInitialized())
104 pybind11_fail("The interpreter is already running");
106 Py_InitializeEx(init_signal_handlers ? 1 : 0);
108 // Make .py files in the working directory available by default
109 module::import("sys").attr("path").cast<list>().append(".");
113 Shut down the Python interpreter. No pybind11 or CPython API functions can be called
114 after this. In addition, pybind11 objects must not outlive the interpreter:
119 py::initialize_interpreter();
120 auto hello = py::str("Hello, World!");
121 py::finalize_interpreter();
122 } // <-- BOOM, hello's destructor is called after interpreter shutdown
125 py::initialize_interpreter();
127 auto hello = py::str("Hello, World!");
128 } // <-- OK, hello is cleaned up properly
129 py::finalize_interpreter();
133 py::scoped_interpreter guard{};
134 auto hello = py::str("Hello, World!");
139 The interpreter can be restarted by calling `initialize_interpreter` again.
140 Modules created using pybind11 can be safely re-initialized. However, Python
141 itself cannot completely unload binary extension modules and there are several
142 caveats with regard to interpreter restarting. All the details can be found
143 in the CPython documentation. In short, not all interpreter memory may be
144 freed, either due to reference cycles or user-created global data.
147 inline void finalize_interpreter() {
148 handle builtins(PyEval_GetBuiltins());
149 const char *id = PYBIND11_INTERNALS_ID;
151 // Get the internals pointer (without creating it if it doesn't exist). It's possible for the
152 // internals to be created during Py_Finalize() (e.g. if a py::capsule calls `get_internals()`
153 // during destruction), so we get the pointer-pointer here and check it after Py_Finalize().
154 detail::internals **internals_ptr_ptr = detail::get_internals_pp();
155 // It could also be stashed in builtins, so look there too:
156 if (builtins.contains(id) && isinstance<capsule>(builtins[id]))
157 internals_ptr_ptr = capsule(builtins[id]);
161 if (internals_ptr_ptr) {
162 delete *internals_ptr_ptr;
163 *internals_ptr_ptr = nullptr;
168 Scope guard version of `initialize_interpreter` and `finalize_interpreter`.
169 This a move-only guard and only a single instance can exist.
173 #include <pybind11/embed.h>
176 py::scoped_interpreter guard{};
177 py::print(Hello, World!);
178 } // <-- interpreter shutdown
180 class scoped_interpreter {
182 scoped_interpreter(bool init_signal_handlers = true) {
183 initialize_interpreter(init_signal_handlers);
186 scoped_interpreter(const scoped_interpreter &) = delete;
187 scoped_interpreter(scoped_interpreter &&other) noexcept { other.is_valid = false; }
188 scoped_interpreter &operator=(const scoped_interpreter &) = delete;
189 scoped_interpreter &operator=(scoped_interpreter &&) = delete;
191 ~scoped_interpreter() {
193 finalize_interpreter();
197 bool is_valid = true;
200 NAMESPACE_END(PYBIND11_NAMESPACE)