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Add C++ interface for the Python interpreter

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This commit is contained in:
Dean Moldovan 2017-03-30 00:20:42 +02:00
parent 9693a5c78f
commit 22c413b196
8 changed files with 263 additions and 50 deletions
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1
CMakeLists.txt
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@ -46,6 +46,7 @@ set(PYBIND11_HEADERS
include/pybind11/descr.h
include/pybind11/options.h
include/pybind11/eigen.h
include/pybind11/embed.h
include/pybind11/eval.h
include/pybind11/functional.h
include/pybind11/numpy.h

11
docs/reference.rst
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@ -58,6 +58,17 @@ Passing extra arguments to ``def`` or ``class_``
.. doxygengroup:: annotations
:members:
Embedding the interpreter
=========================
.. doxygendefine:: PYBIND11_EMBEDDED_MODULE
.. doxygenfunction:: initialize_interpreter
.. doxygenfunction:: finalize_interpreter
.. doxygenclass:: scoped_interpreter
Python build-in functions
=========================

175
include/pybind11/embed.h Normal file
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@ -0,0 +1,175 @@
/*
pybind11/embed.h: Support for embedding the interpreter
Copyright (c) 2017 Wenzel Jakob <wenzel.jakob@epfl.ch>
All rights reserved. Use of this source code is governed by a
BSD-style license that can be found in the LICENSE file.
*/
#pragma once
#include "pybind11.h"
#include "eval.h"
#if defined(PYPY_VERSION)
# error Embedding the interpreter is not supported with PyPy
#endif
#if PY_MAJOR_VERSION >= 3
# define PYBIND11_EMBEDDED_MODULE_IMPL(name) \
extern "C" PyObject *pybind11_init_impl_##name() { \
return pybind11_init_wrapper_##name(); \
}
#else
# define PYBIND11_EMBEDDED_MODULE_IMPL(name) \
extern "C" void pybind11_init_impl_##name() { \
pybind11_init_wrapper_##name(); \
}
#endif
/** \rst
Add a new module to the table of builtins for the interpreter. Must be
defined in global scope. The first macro parameter is the name of the
module (without quotes). The second parameter is the variable which will
be used as the interface to add functions and classes to the module.
.. code-block:: cpp
PYBIND11_EMBEDDED_MODULE(example, m) {
// ... initialize functions and classes here
m.def("foo", []() {
return "Hello, World!";
});
}
\endrst */
#define PYBIND11_EMBEDDED_MODULE(name, variable) \
static void pybind11_init_##name(pybind11::module &); \
static PyObject *pybind11_init_wrapper_##name() { \
auto m = pybind11::module(#name); \
try { \
pybind11_init_##name(m); \
return m.ptr(); \
} catch (pybind11::error_already_set &e) { \
e.clear(); \
PyErr_SetString(PyExc_ImportError, e.what()); \
return nullptr; \
} catch (const std::exception &e) { \
PyErr_SetString(PyExc_ImportError, e.what()); \
return nullptr; \
} \
} \
PYBIND11_EMBEDDED_MODULE_IMPL(name) \
pybind11::detail::embedded_module name(#name, pybind11_init_impl_##name); \
void pybind11_init_##name(pybind11::module &variable)
NAMESPACE_BEGIN(pybind11)
NAMESPACE_BEGIN(detail)
/// Python 2.7/3.x compatible version of `PyImport_AppendInittab` and error checks.
struct embedded_module {
#if PY_MAJOR_VERSION >= 3
using init_t = PyObject *(*)();
#else
using init_t = void (*)();
#endif
embedded_module(const char *name, init_t init) {
if (Py_IsInitialized())
pybind11_fail("Can't add new modules after the interpreter has been initialized");
auto result = PyImport_AppendInittab(name, init);
if (result == -1)
pybind11_fail("Insufficient memory to add a new module");
}
};
NAMESPACE_END(detail)
/** \rst
Initialize the Python interpreter. No other pybind11 or CPython API functions can be
called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
optional parameter can be used to skip the registration of signal handlers (see the
Python documentation for details). Calling this function again after the interpreter
has already been initialized is a fatal error.
\endrst */
inline void initialize_interpreter(bool init_signal_handlers = true) {
if (Py_IsInitialized())
pybind11_fail("The interpreter is already running");
Py_InitializeEx(init_signal_handlers ? 1 : 0);
// Make .py files in the working directory available by default
auto sys_path = reinterpret_borrow<list>(module::import("sys").attr("path"));
sys_path.append(".");
}
/** \rst
Shut down the Python interpreter. No pybind11 or CPython API functions can be called
after this. In addition, pybind11 objects must not outlive the interpreter:
.. code-block:: cpp
{ // BAD
py::initialize_interpreter();
auto hello = py::str("Hello, World!");
py::finalize_interpreter();
} // <-- BOOM, hello's destructor is called after interpreter shutdown
{ // GOOD
py::initialize_interpreter();
{ // scoped
auto hello = py::str("Hello, World!");
} // <-- OK, hello is cleaned up properly
py::finalize_interpreter();
}
{ // BETTER
py::scoped_interpreter guard{};
auto hello = py::str("Hello, World!");
}
.. warning::
Python cannot unload binary extension modules. If `initialize_interpreter` is
called again to restart the interpreter, the initializers of those modules will
be executed for a second time and they will fail. This is a known CPython issue.
See the Python documentation for details.
\endrst */
inline void finalize_interpreter() { Py_Finalize(); }
/** \rst
Scope guard version of `initialize_interpreter` and `finalize_interpreter`.
This a move-only guard and only a single instance can exist.
.. code-block:: cpp
#include <pybind11/embed.h>
int main() {
py::scoped_interpreter guard{};
py::print(Hello, World!);
} // <-- interpreter shutdown
\endrst */
class scoped_interpreter {
public:
scoped_interpreter(bool init_signal_handlers = true) {
initialize_interpreter(init_signal_handlers);
}
scoped_interpreter(const scoped_interpreter &) = delete;
scoped_interpreter(scoped_interpreter &&other) noexcept { other.is_valid = false; }
scoped_interpreter &operator=(const scoped_interpreter &) = delete;
scoped_interpreter &operator=(scoped_interpreter &&) = delete;
~scoped_interpreter() {
if (is_valid)
finalize_interpreter();
}
private:
bool is_valid = true;
};
NAMESPACE_END(pybind11)

4
include/pybind11/pybind11.h
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@ -798,6 +798,10 @@ public:
}
};
/// \ingroup python_builtins
/// Return a dictionary representing the global symbol table, i.e. ``__main__.__dict__``.
inline dict globals() { return module::import("__main__").attr("__dict__").cast<dict>(); }
NAMESPACE_BEGIN(detail)
/// Generic support for creating new Python heap types
class generic_type : public object {

1
setup.py
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@ -21,6 +21,7 @@ else:
'include/pybind11/complex.h',
'include/pybind11/descr.h',
'include/pybind11/eigen.h',
'include/pybind11/embed.h',
'include/pybind11/eval.h',
'include/pybind11/functional.h',
'include/pybind11/numpy.h',

27
tests/test_cmake_build/embed.cpp
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@ -1,13 +1,8 @@
#include <pybind11/pybind11.h>
#include <pybind11/eval.h>
#include <pybind11/embed.h>
namespace py = pybind11;
PyObject *make_module() {
py::module m("test_cmake_build");
PYBIND11_EMBEDDED_MODULE(test_cmake_build, m) {
m.def("add", [](int i, int j) { return i + j; });
return m.ptr();
}
int main(int argc, char *argv[]) {
@ -15,16 +10,12 @@ int main(int argc, char *argv[]) {
throw std::runtime_error("Expected test.py file as the first argument");
auto test_py_file = argv[1];
PyImport_AppendInittab("test_cmake_build", &make_module);
Py_Initialize();
{
auto m = py::module::import("test_cmake_build");
if (m.attr("add")(1, 2).cast<int>() != 3)
throw std::runtime_error("embed.cpp failed");
py::scoped_interpreter guard{};
auto globals = py::module::import("__main__").attr("__dict__");
py::module::import("sys").attr("argv") = py::make_tuple("test.py", "embed.cpp");
py::eval_file(test_py_file, globals);
}
Py_Finalize();
auto m = py::module::import("test_cmake_build");
if (m.attr("add")(1, 2).cast<int>() != 3)
throw std::runtime_error("embed.cpp failed");
py::module::import("sys").attr("argv") = py::make_tuple("test.py", "embed.cpp");
py::eval_file(test_py_file, py::globals());
}

15
tests/test_embed/catch.cpp
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@ -1,5 +1,16 @@
// Catch provides the `int main()` function here. This is a standalone
// The Catch implementation is compiled here. This is a standalone
// translation unit to avoid recompiling it for every test change.
#define CATCH_CONFIG_MAIN
#include <pybind11/embed.h>
#define CATCH_CONFIG_RUNNER
#include <catch.hpp>
namespace py = pybind11;
int main(int argc, const char *argv[]) {
py::scoped_interpreter guard{};
auto result = Catch::Session().run(argc, argv);
return result < 0xff ? result : 0xff;
}

79
tests/test_embed/test_interpreter.cpp
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@ -1,6 +1,4 @@
#include <pybind11/pybind11.h>
#include <pybind11/eval.h>
#include <pybind11/embed.h>
#include <catch.hpp>
namespace py = pybind11;
@ -24,41 +22,62 @@ class PyWidget final : public Widget {
int the_answer() const override { PYBIND11_OVERLOAD_PURE(int, Widget, the_answer); }
};
PyObject *make_embedded_module() {
py::module m("widget_module");
PYBIND11_EMBEDDED_MODULE(widget_module, m) {
py::class_<Widget, PyWidget>(m, "Widget")
.def(py::init<std::string>())
.def_property_readonly("the_message", &Widget::the_message);
return m.ptr();
}
py::object import_file(const std::string &module, const std::string &path, py::object globals) {
auto locals = py::dict("module_name"_a=module, "path"_a=path);
py::eval<py::eval_statements>(
"import imp\n"
"with open(path) as file:\n"
" new_module = imp.load_module(module_name, file, path, ('py', 'U', imp.PY_SOURCE))",
globals, locals
);
return locals["new_module"];
PYBIND11_EMBEDDED_MODULE(throw_exception, ) {
throw std::runtime_error("C++ Error");
}
PYBIND11_EMBEDDED_MODULE(throw_error_already_set, ) {
auto d = py::dict();
d["missing"].cast<py::object>();
}
TEST_CASE("Pass classes and data between modules defined in C++ and Python") {
PyImport_AppendInittab("widget_module", &make_embedded_module);
Py_Initialize();
{
auto globals = py::module::import("__main__").attr("__dict__");
auto module = import_file("widget", "test_interpreter.py", globals);
REQUIRE(py::hasattr(module, "DerivedWidget"));
auto module = py::module::import("test_interpreter");
REQUIRE(py::hasattr(module, "DerivedWidget"));
auto py_widget = module.attr("DerivedWidget")("Hello, World!");
auto message = py_widget.attr("the_message");
REQUIRE(message.cast<std::string>() == "Hello, World!");
auto locals = py::dict("hello"_a="Hello, World!", "x"_a=5, **module.attr("__dict__"));
py::exec(R"(
widget = DerivedWidget("{} - {}".format(hello, x))
message = widget.the_message
)", py::globals(), locals);
REQUIRE(locals["message"].cast<std::string>() == "Hello, World! - 5");
const auto &cpp_widget = py_widget.cast<const Widget &>();
REQUIRE(cpp_widget.the_answer() == 42);
}
Py_Finalize();
auto py_widget = module.attr("DerivedWidget")("The question");
auto message = py_widget.attr("the_message");
REQUIRE(message.cast<std::string>() == "The question");
const auto &cpp_widget = py_widget.cast<const Widget &>();
REQUIRE(cpp_widget.the_answer() == 42);
}
TEST_CASE("Import error handling") {
REQUIRE_NOTHROW(py::module::import("widget_module"));
REQUIRE_THROWS_WITH(py::module::import("throw_exception"),
"ImportError: C++ Error");
REQUIRE_THROWS_WITH(py::module::import("throw_error_already_set"),
Catch::Contains("ImportError: KeyError"));
}
TEST_CASE("There can be only one interpreter") {
static_assert(std::is_move_constructible<py::scoped_interpreter>::value, "");
static_assert(!std::is_move_assignable<py::scoped_interpreter>::value, "");
static_assert(!std::is_copy_constructible<py::scoped_interpreter>::value, "");
static_assert(!std::is_copy_assignable<py::scoped_interpreter>::value, "");
REQUIRE_THROWS_WITH(py::initialize_interpreter(), "The interpreter is already running");
REQUIRE_THROWS_WITH(py::scoped_interpreter(), "The interpreter is already running");
py::finalize_interpreter();
REQUIRE_NOTHROW(py::scoped_interpreter());
{
auto pyi1 = py::scoped_interpreter();
auto pyi2 = std::move(pyi1);
}
py::initialize_interpreter();
}