Add preliminary binding example for systems framework.

WORKSPACE

@@ -237,9 +237,10 @@ github_archive(
 
 github_archive(
     name = "pybind11",
-    repository = "RobotLocomotion/pybind11",
-    commit = "ffcf754ae9e766632610975d22372a86a7b63014",
-    sha256 = "7cd6f4efb02bf9ae17eeb2afba68023af913e61ae76e8b4254203d0eec019525",  # noqa
+    # TODO(eric.cousineau): Merge this with RobotLocomotion.
+    repository = "EricCousineau-TRI/pybind11",
+    commit = "b7e92676552dc73613c8e18624091fa9ffd4fa54",
+    sha256 = "464d35d81c680ea251f3c09d6f1f2fef34e9696c49865a6cea193d6a0de9caf9",  # noqa
     build_file = "tools/workspace/pybind11/pybind11.BUILD.bazel",
 )
 

bindings/pydrake/systems/BUILD.bazel

@@ -0,0 +1,115 @@
+# -*- python -*-
+
+load("@drake//tools/install:install.bzl", "install")
+load("//tools/lint:lint.bzl", "add_lint_tests")
+load(
+    "//tools/skylark:pybind.bzl",
+    "drake_pybind_library",
+    "get_drake_pybind_installs",
+    "get_pybind_library_dest",
+)
+load(
+    "//tools/skylark:drake_py.bzl",
+    "drake_py_binary",
+    "drake_py_library",
+    "drake_py_test",
+)
+load("//tools/skylark:6996.bzl", "adjust_labels_for_drake_hoist")
+
+package(default_visibility = adjust_labels_for_drake_hoist([
+    "//drake/bindings/pydrake:__subpackages__",
+]))
+
+drake_py_library(
+    name = "module_py",
+    srcs = ["__init__.py"],
+    deps = [
+        "//drake/bindings/pydrake:common_py",
+        # TODO(eric.cousineau): This does NOT include direct dependencies to
+        # submodule. This is to preserve C++-like namespaces.
+    ],
+)
+
+drake_pybind_library(
+    name = "framework_py",
+    cc_so_name = "framework",
+    cc_srcs = ["framework_py.cc"],
+    py_deps = [
+        ":module_py",
+    ],
+)
+
+drake_pybind_library(
+    name = "primitives_py",
+    cc_so_name = "primitives",
+    cc_srcs = ["primitives_py.cc"],
+    py_deps = [
+        ":framework_py",
+        ":module_py",
+    ],
+)
+
+drake_pybind_library(
+    name = "analysis_py",
+    cc_so_name = "analysis",
+    cc_srcs = ["analysis_py.cc"],
+    py_deps = [
+        ":framework_py",
+        ":module_py",
+    ],
+)
+
+drake_py_library(
+    name = "drawing_py",
+    srcs = ["drawing.py"],
+    deps = [":module_py"],
+    # TODO(eric.cousineau): Expose information to allow `imports = ...` to be
+    # defined, rather than rely on `module_py`.
+)
+
+PYBIND_LIBRARIES = [
+    ":analysis_py",
+    ":framework_py",
+    ":primitives_py",
+]
+
+PY_LIBRARIES = [
+    ":drawing_py",
+    ":module_py",
+]
+
+drake_py_library(
+    name = "systems",
+    deps = PYBIND_LIBRARIES + PY_LIBRARIES,
+)
+
+install(
+    name = "install",
+    targets = PY_LIBRARIES,
+    py_dest = get_pybind_library_dest(),
+    deps = get_drake_pybind_installs(PYBIND_LIBRARIES),
+)
+
+drake_py_test(
+    name = "system_general_test",
+    size = "small",
+    srcs = ["test/system_general_test.py"],
+    deps = [
+        ":analysis_py",
+        ":framework_py",
+        ":primitives_py",
+    ],
+)
+
+drake_py_binary(
+    name = "system_graphviz_example",
+    srcs = ["test/system_graphviz_example.py"],
+    deps = [
+        ":analysis_py",
+        ":drawing_py",
+        ":framework_py",
+        ":primitives_py",
+    ],
+)
+
+add_lint_tests()

bindings/pydrake/systems/__init__.py

@@ -0,0 +1,23 @@
+from __future__ import absolute_import, print_function
+
+# TODO(eric.cousineau): Should we attempt to modularize this dependency graph?
+# How about separating this setup (development) from a more pure approach
+# (deployment)?
+
+try:
+    from .analysis import *
+except ImportError as e:
+    print(e)
+    pass
+
+try:
+    from .framework import *
+except ImportError as e:
+    print(e)
+    pass
+
+try:
+    from .primitives import *
+except ImportError as e:
+    print(e)
+    pass

bindings/pydrake/systems/analysis_py.cc

@@ -0,0 +1,25 @@
+#include <pybind11/pybind11.h>
+
+#include "drake/systems/analysis/simulator.h"
+
+namespace py = pybind11;
+
+using std::unique_ptr;
+
+PYBIND11_MODULE(analysis, m) {
+  // NOLINTNEXTLINE(build/namespaces): Emulate placement in namespace.
+  using namespace drake::systems;
+
+  auto py_iref = py::return_value_policy::reference_internal;
+
+  m.doc() = "Bindings for the analysis portion of the Systems framework.";
+
+  using T = double;
+
+  py::class_<Simulator<T>>(m, "Simulator")
+    .def(py::init<const System<T>&>())
+    .def(py::init<const System<T>&, unique_ptr<Context<T>>>())
+    .def("Initialize", &Simulator<T>::Initialize)
+    .def("StepTo", &Simulator<T>::StepTo)
+    .def("get_mutable_context", &Simulator<T>::get_mutable_context, py_iref);
+}

bindings/pydrake/systems/drawing.py

@@ -0,0 +1,33 @@
+# @file
+# Provides general visualization utilities. This is NOT related to `rendering`.
+# @note This is an optional module, dependent on `pydot` and `matplotlib` being
+# installed.
+
+from StringIO import StringIO
+
+import matplotlib.image as mpimg
+import matplotlib.pyplot as plt
+import pydot
+
+
+# TODO(eric.cousineau): Move `plot_graphviz` to something more accessible to
+# `call_python_client`.
+
+
+def plot_graphviz(dot_text):
+    """Renders a DOT graph in matplotlib."""
+    # @ref https://stackoverflow.com/a/18522941/7829525
+    # Tried (reason ignored): pydotplus (`pydot` works), networkx
+    # (`read_dot` does not work robustly?), pygraphviz (coupled with
+    # `networkx`).
+    g = pydot.graph_from_dot_data(dot_text)
+    s = StringIO()
+    g.write_png(s)
+    s.seek(0)
+    plt.axis('off')
+    return plt.imshow(plt.imread(s), aspect="equal")
+
+
+def plot_system_graphviz(system):
+    """Renders a System's Graphviz representation in `matplotlib`. """
+    return plot_graphviz(system.GetGraphvizString())

bindings/pydrake/systems/framework_py.cc

@@ -0,0 +1,151 @@
+#include <pybind11/eigen.h>
+#include <pybind11/eval.h>
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+
+#include "drake/common/nice_type_name.h"
+#include "drake/systems/framework/abstract_values.h"
+#include "drake/systems/framework/basic_vector.h"
+#include "drake/systems/framework/context.h"
+#include "drake/systems/framework/diagram.h"
+#include "drake/systems/framework/diagram_builder.h"
+#include "drake/systems/framework/leaf_context.h"
+#include "drake/systems/framework/leaf_system.h"
+#include "drake/systems/framework/output_port_value.h"
+#include "drake/systems/framework/subvector.h"
+#include "drake/systems/framework/supervector.h"
+#include "drake/systems/framework/system.h"
+
+namespace py = pybind11;
+
+using std::make_unique;
+using std::unique_ptr;
+using std::vector;
+
+PYBIND11_MODULE(framework, m) {
+  // NOLINTNEXTLINE(build/namespaces): Emulate placement in namespace.
+  using namespace drake;
+  // NOLINTNEXTLINE(build/namespaces): Emulate placement in namespace.
+  using namespace drake::systems;
+
+  // Aliases for commonly used return value policies.
+  // `py_ref` is used when `keep_alive` is explicitly used (e.g. for extraction
+  // methods, like `GetMutableSubsystemState`).
+  auto py_ref = py::return_value_policy::reference;
+  // `py_iref` is used when pointers / lvalue references are returned (no need
+  // for `keep_alive`, as it is implicit.
+  auto py_iref = py::return_value_policy::reference_internal;
+
+  m.doc() = "Bindings for the core Systems framework.";
+
+  // TODO(eric.cousineau): At present, we only bind doubles.
+  // In the future, we will bind more scalar types, and enable scalar
+  // conversion.
+  using T = double;
+
+  // TODO(eric.cousineau): Resolve `str_py` workaround.
+  auto str_py = py::eval("str");
+
+  // TODO(eric.cousineau): Show constructor, but somehow make sure `pybind11`
+  // knows this is abstract?
+  py::class_<System<T>>(m, "System")
+    .def("set_name", &System<T>::set_name)
+    .def("get_input_port", &System<T>::get_input_port, py_iref)
+    .def("get_output_port", &System<T>::get_output_port, py_iref)
+    .def("CreateDefaultContext", &System<T>::CreateDefaultContext)
+    .def("AllocateOutput", &System<T>::AllocateOutput)
+    .def(
+        "GetGraphvizString",
+        [str_py](const System<T>* self) {
+          // @note This is a workaround; for some reason,
+          // casting this using `py::str` does not work, but directly
+          // calling the Python function (`str_py`) does.
+          return str_py(self->GetGraphvizString());
+        });
+
+  py::class_<LeafSystem<T>, System<T>>(m, "LeafSystem");
+
+  py::class_<Context<T>>(m, "Context")
+    .def("FixInputPort",
+         py::overload_cast<int, unique_ptr<BasicVector<T>>>(
+             &Context<T>::FixInputPort))
+    .def("get_time", &Context<T>::get_time)
+    .def("Clone", &Context<T>::Clone)
+    .def("__copy__", &Context<T>::Clone)
+    .def("get_state", &Context<T>::get_state, py_iref)
+    .def("get_mutable_state", &Context<T>::get_mutable_state, py_iref);
+
+  py::class_<LeafContext<T>, Context<T>>(m, "LeafContext");
+
+  py::class_<Diagram<T>, System<T>>(m, "Diagram")
+    .def("GetMutableSubsystemState",
+        [](Diagram<T>* self, const System<T>& arg1, Context<T>* arg2)
+        -> auto&& {
+          // @note Use `auto&&` to get perfect forwarding.
+          // @note Compiler does not like `py::overload_cast` with this setup?
+          return self->GetMutableSubsystemState(arg1, arg2);
+        }, py_ref, py::keep_alive<0, 3>());
+
+  // Glue mechanisms.
+  py::class_<DiagramBuilder<T>>(m, "DiagramBuilder")
+    .def(py::init<>())
+    .def(
+        "AddSystem",
+        [](DiagramBuilder<T>* self, unique_ptr<System<T>> arg1) {
+          return self->AddSystem(std::move(arg1));
+        })
+    .def("Connect",
+         py::overload_cast<const OutputPort<T>&, const InputPortDescriptor<T>&>(
+             &DiagramBuilder<T>::Connect))
+    .def("ExportInput", &DiagramBuilder<T>::ExportInput)
+    .def("ExportOutput", &DiagramBuilder<T>::ExportOutput)
+    .def("Build", &DiagramBuilder<T>::Build)
+    .def("BuildInto", &DiagramBuilder<T>::BuildInto);
+
+  py::class_<OutputPort<T>>(m, "OutputPort");
+  py::class_<SystemOutput<T>>(m, "SystemOutput");
+
+  py::class_<InputPortDescriptor<T>>(m, "InputPortDescriptor");
+
+  // Value types.
+  py::class_<VectorBase<T>>(m, "VectorBase")
+    .def("CopyToVector", &VectorBase<T>::CopyToVector)
+    .def("SetFromVector", &VectorBase<T>::SetFromVector);
+
+  py::class_<BasicVector<T>, VectorBase<T>>(m, "BasicVector")
+    .def(py::init<VectorX<T>>())
+    .def("get_value", &BasicVector<T>::get_value);
+
+  py::class_<Supervector<T>, VectorBase<T>>(m, "Supervector");
+
+  py::class_<Subvector<T>, VectorBase<T>>(m, "Subvector");
+
+  // TODO(eric.cousineau): Interfacing with the C++ abstract value types may be
+  // a tad challenging. This should be more straightforward once
+  // scalar-type conversion is supported, as the template-exposure mechanisms
+  // should be relatively similar.
+  py::class_<AbstractValue>(m, "AbstractValue");
+
+  // Parameters.
+  // TODO(eric.cousineau): Fill this out.
+  py::class_<Parameters<T>>(m, "Parameters");
+
+  // State.
+  py::class_<State<T>>(m, "State")
+    .def(py::init<>())
+    .def("get_continuous_state",
+         &State<T>::get_continuous_state, py_iref)
+    .def("get_mutable_continuous_state",
+         &State<T>::get_mutable_continuous_state, py_iref);
+
+  // - Constituents.
+  py::class_<ContinuousState<T>>(m, "ContinuousState")
+    .def(py::init<>())
+    .def("get_vector", &ContinuousState<T>::get_vector, py_iref)
+    .def("get_mutable_vector",
+         &ContinuousState<T>::get_mutable_vector, py_iref);
+
+  py::class_<DiscreteValues<T>>(m, "DiscreteValues");
+
+  py::class_<AbstractValues>(m, "AbstractValues");
+}

bindings/pydrake/systems/primitives_py.cc

@@ -0,0 +1,31 @@
+#include <pybind11/eigen.h>
+#include <pybind11/pybind11.h>
+
+#include "drake/systems/primitives/adder.h"
+#include "drake/systems/primitives/constant_value_source.h"
+#include "drake/systems/primitives/constant_vector_source.h"
+#include "drake/systems/primitives/integrator.h"
+
+namespace py = pybind11;
+
+PYBIND11_MODULE(primitives, m) {
+  // NOLINTNEXTLINE(build/namespaces): Emulate placement in namespace.
+  using namespace drake;
+  // NOLINTNEXTLINE(build/namespaces): Emulate placement in namespace.
+  using namespace drake::systems;
+
+  m.doc() = "Bindings for the primitives portion of the Systems framework.";
+
+  using T = double;
+
+  py::class_<ConstantVectorSource<T>, LeafSystem<T>>(m, "ConstantVectorSource")
+    .def(py::init<VectorX<T>>());
+
+  py::class_<ConstantValueSource<T>, LeafSystem<T>>(m, "ConstantValueSource");
+
+  py::class_<Adder<T>, LeafSystem<T>>(m, "Adder")
+    .def(py::init<int, int>());
+
+  py::class_<Integrator<T>, LeafSystem<T>>(m, "Integrator")
+    .def(py::init<int>());
+}