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 extern "C" PyObject *pybind11_init_impl_##name() { \
23 return pybind11_init_wrapper_##name(); \
26 # define PYBIND11_EMBEDDED_MODULE_IMPL(name) \
27 extern "C" void pybind11_init_impl_##name(); \
28 extern "C" void pybind11_init_impl_##name() { \
29 pybind11_init_wrapper_##name(); \
34 Add a new module to the table of builtins for the interpreter. Must be
35 defined in global scope. The first macro parameter is the name of the
36 module (without quotes). The second parameter is the variable which will
37 be used as the interface to add functions and classes to the module.
41 PYBIND11_EMBEDDED_MODULE(example, m) {
42 // ... initialize functions and classes here
44 return "Hello, World!";
48 #define PYBIND11_EMBEDDED_MODULE(name, variable) \
49 static void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &); \
50 static PyObject PYBIND11_CONCAT(*pybind11_init_wrapper_, name)() { \
51 auto m = pybind11::module(PYBIND11_TOSTRING(name)); \
53 PYBIND11_CONCAT(pybind11_init_, name)(m); \
55 } catch (pybind11::error_already_set &e) { \
56 PyErr_SetString(PyExc_ImportError, e.what()); \
58 } catch (const std::exception &e) { \
59 PyErr_SetString(PyExc_ImportError, e.what()); \
63 PYBIND11_EMBEDDED_MODULE_IMPL(name) \
64 pybind11::detail::embedded_module name(PYBIND11_TOSTRING(name), \
65 PYBIND11_CONCAT(pybind11_init_impl_, name)); \
66 void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &variable)
69 NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
70 NAMESPACE_BEGIN(detail)
72 /// Python 2.7/3.x compatible version of `PyImport_AppendInittab` and error checks.
73 struct embedded_module {
74 #if PY_MAJOR_VERSION >= 3
75 using init_t = PyObject *(*)();
77 using init_t = void (*)();
79 embedded_module(const char *name, init_t init) {
80 if (Py_IsInitialized())
81 pybind11_fail("Can't add new modules after the interpreter has been initialized");
83 auto result = PyImport_AppendInittab(name, init);
85 pybind11_fail("Insufficient memory to add a new module");
92 Initialize the Python interpreter. No other pybind11 or CPython API functions can be
93 called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
94 optional parameter can be used to skip the registration of signal handlers (see the
95 `Python documentation`_ for details). Calling this function again after the interpreter
96 has already been initialized is a fatal error.
98 If initializing the Python interpreter fails, then the program is terminated. (This
99 is controlled by the CPython runtime and is an exception to pybind11's normal behavior
100 of throwing exceptions on errors.)
102 .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
104 inline void initialize_interpreter(bool init_signal_handlers = true) {
105 if (Py_IsInitialized())
106 pybind11_fail("The interpreter is already running");
108 Py_InitializeEx(init_signal_handlers ? 1 : 0);
110 // Make .py files in the working directory available by default
111 module::import("sys").attr("path").cast<list>().append(".");
115 Shut down the Python interpreter. No pybind11 or CPython API functions can be called
116 after this. In addition, pybind11 objects must not outlive the interpreter:
121 py::initialize_interpreter();
122 auto hello = py::str("Hello, World!");
123 py::finalize_interpreter();
124 } // <-- BOOM, hello's destructor is called after interpreter shutdown
127 py::initialize_interpreter();
129 auto hello = py::str("Hello, World!");
130 } // <-- OK, hello is cleaned up properly
131 py::finalize_interpreter();
135 py::scoped_interpreter guard{};
136 auto hello = py::str("Hello, World!");
141 The interpreter can be restarted by calling `initialize_interpreter` again.
142 Modules created using pybind11 can be safely re-initialized. However, Python
143 itself cannot completely unload binary extension modules and there are several
144 caveats with regard to interpreter restarting. All the details can be found
145 in the CPython documentation. In short, not all interpreter memory may be
146 freed, either due to reference cycles or user-created global data.
149 inline void finalize_interpreter() {
150 handle builtins(PyEval_GetBuiltins());
151 const char *id = PYBIND11_INTERNALS_ID;
153 // Get the internals pointer (without creating it if it doesn't exist). It's possible for the
154 // internals to be created during Py_Finalize() (e.g. if a py::capsule calls `get_internals()`
155 // during destruction), so we get the pointer-pointer here and check it after Py_Finalize().
156 detail::internals **internals_ptr_ptr = detail::get_internals_pp();
157 // It could also be stashed in builtins, so look there too:
158 if (builtins.contains(id) && isinstance<capsule>(builtins[id]))
159 internals_ptr_ptr = capsule(builtins[id]);
163 if (internals_ptr_ptr) {
164 delete *internals_ptr_ptr;
165 *internals_ptr_ptr = nullptr;
170 Scope guard version of `initialize_interpreter` and `finalize_interpreter`.
171 This a move-only guard and only a single instance can exist.
175 #include <pybind11/embed.h>
178 py::scoped_interpreter guard{};
179 py::print(Hello, World!);
180 } // <-- interpreter shutdown
182 class scoped_interpreter {
184 scoped_interpreter(bool init_signal_handlers = true) {
185 initialize_interpreter(init_signal_handlers);
188 scoped_interpreter(const scoped_interpreter &) = delete;
189 scoped_interpreter(scoped_interpreter &&other) noexcept { other.is_valid = false; }
190 scoped_interpreter &operator=(const scoped_interpreter &) = delete;
191 scoped_interpreter &operator=(scoped_interpreter &&) = delete;
193 ~scoped_interpreter() {
195 finalize_interpreter();
199 bool is_valid = true;
202 NAMESPACE_END(PYBIND11_NAMESPACE)