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 inline void initialize_interpreter(bool init_signal_handlers = true) {
97 if (Py_IsInitialized())
98 pybind11_fail("The interpreter is already running");
100 Py_InitializeEx(init_signal_handlers ? 1 : 0);
102 // Make .py files in the working directory available by default
103 module::import("sys").attr("path").cast<list>().append(".");
107 Shut down the Python interpreter. No pybind11 or CPython API functions can be called
108 after this. In addition, pybind11 objects must not outlive the interpreter:
113 py::initialize_interpreter();
114 auto hello = py::str("Hello, World!");
115 py::finalize_interpreter();
116 } // <-- BOOM, hello's destructor is called after interpreter shutdown
119 py::initialize_interpreter();
121 auto hello = py::str("Hello, World!");
122 } // <-- OK, hello is cleaned up properly
123 py::finalize_interpreter();
127 py::scoped_interpreter guard{};
128 auto hello = py::str("Hello, World!");
133 The interpreter can be restarted by calling `initialize_interpreter` again.
134 Modules created using pybind11 can be safely re-initialized. However, Python
135 itself cannot completely unload binary extension modules and there are several
136 caveats with regard to interpreter restarting. All the details can be found
137 in the CPython documentation. In short, not all interpreter memory may be
138 freed, either due to reference cycles or user-created global data.
141 inline void finalize_interpreter() {
142 handle builtins(PyEval_GetBuiltins());
143 const char *id = PYBIND11_INTERNALS_ID;
145 // Get the internals pointer (without creating it if it doesn't exist). It's possible for the
146 // internals to be created during Py_Finalize() (e.g. if a py::capsule calls `get_internals()`
147 // during destruction), so we get the pointer-pointer here and check it after Py_Finalize().
148 detail::internals **internals_ptr_ptr = detail::get_internals_pp();
149 // It could also be stashed in builtins, so look there too:
150 if (builtins.contains(id) && isinstance<capsule>(builtins[id]))
151 internals_ptr_ptr = capsule(builtins[id]);
155 if (internals_ptr_ptr) {
156 delete *internals_ptr_ptr;
157 *internals_ptr_ptr = nullptr;
162 Scope guard version of `initialize_interpreter` and `finalize_interpreter`.
163 This a move-only guard and only a single instance can exist.
167 #include <pybind11/embed.h>
170 py::scoped_interpreter guard{};
171 py::print(Hello, World!);
172 } // <-- interpreter shutdown
174 class scoped_interpreter {
176 scoped_interpreter(bool init_signal_handlers = true) {
177 initialize_interpreter(init_signal_handlers);
180 scoped_interpreter(const scoped_interpreter &) = delete;
181 scoped_interpreter(scoped_interpreter &&other) noexcept { other.is_valid = false; }
182 scoped_interpreter &operator=(const scoped_interpreter &) = delete;
183 scoped_interpreter &operator=(scoped_interpreter &&) = delete;
185 ~scoped_interpreter() {
187 finalize_interpreter();
191 bool is_valid = true;
194 NAMESPACE_END(PYBIND11_NAMESPACE)