python: Add access to the property_tree from Python

Example:
>>> usrp = uhd.usrp.multi_usrp("")
>>> tree = usrp.get_tree()
>>> print(tree.access_int("/name").get())

host/lib/property_tree_python.cpp

@@ -0,0 +1,61 @@
+//
+// Copyright 2020 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#include "property_tree_python.hpp"
+#include <uhd/property_tree.hpp>
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+#include <string>
+
+namespace py = pybind11;
+
+template <typename T>
+void export_property(py::module& m, const std::string& type_str)
+{
+    const std::string classname = std::string("property__") + type_str;
+    py::class_<uhd::property<T>>(m, classname.c_str())
+        .def("get", &uhd::property<T>::get)
+        .def("get_desired", &uhd::property<T>::get_desired)
+        .def("set", &uhd::property<T>::set)
+        .def("set_coerced", &uhd::property<T>::set_coerced);
+}
+
+void export_property_tree(py::module& m)
+{
+    using property_tree = uhd::property_tree;
+    using fs_path = uhd::fs_path;
+
+    py::class_<fs_path>(m, "fs_path")
+        // Constructors
+        .def(py::init<>())
+        .def(py::init<std::string>());
+    py::implicitly_convertible<std::string, fs_path>();
+
+    // Per type we want to expose, add one line here, and one accessor below
+    export_property<int>(m, "int");
+    export_property<double>(m, "double");
+    export_property<std::string>(m, "str");
+    export_property<bool>(m, "bool");
+
+    py::class_<property_tree>(m, "property_tree")
+        .def("subtree", &property_tree::subtree, py::arg("path"))
+        .def("exists", &property_tree::exists, py::arg("path"))
+        .def("list", &property_tree::list, py::arg("path"))
+        // One line per type
+        .def(
+            "access_int", &property_tree::access<int>, py::return_value_policy::reference)
+        .def("access_double",
+            &property_tree::access<double>,
+            py::return_value_policy::reference)
+        .def("access_str",
+            &property_tree::access<std::string>,
+            py::return_value_policy::reference)
+        .def("access_bool",
+            &property_tree::access<bool>,
+            py::return_value_policy::reference)
+        // End of types
+        ;
+}

host/lib/property_tree_python.hpp

@@ -0,0 +1,11 @@
+//
+// Copyright 2020 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#pragma once
+
+#include <pybind11/pybind11.h>
+
+void export_property_tree(pybind11::module& m);

host/lib/usrp/multi_usrp_python.cpp

@@ -5,7 +5,9 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 //
 
+#include <pybind11/complex.h>
 #include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
 
 namespace py = pybind11;
 
@@ -27,6 +29,8 @@ void export_multi_usrp(py::module& m)
         .def(py::init(&multi_usrp::make))
 
         // clang-format off
+        .def("get_tree"                , &multi_usrp::get_tree)
+
         // General USRP methods
         .def("get_rx_freq"             , &multi_usrp::get_rx_freq, py::arg("chan") = 0)
         .def("get_rx_num_channels"     , &multi_usrp::get_rx_num_channels)

host/python/CMakeLists.txt

@@ -31,6 +31,7 @@ execute_process(
 # Build pyuhd library
 add_library(pyuhd SHARED
     pyuhd.cpp
+    ${CMAKE_SOURCE_DIR}/lib/property_tree_python.cpp
     ${CMAKE_SOURCE_DIR}/lib/usrp/multi_usrp_python.cpp
 )
 # python expects extension modules with a particular suffix

host/python/pyuhd.cpp

@@ -14,6 +14,7 @@
 namespace py = pybind11;
 
 #include "cal/cal_python.hpp"
+#include "property_tree_python.hpp"
 #include "rfnoc/ddc_block_control_python.hpp"
 #include "rfnoc/duc_block_control_python.hpp"
 #include "rfnoc/fft_block_control_python.hpp"
@@ -110,4 +111,7 @@ PYBIND11_MODULE(libpyuhd, m)
 
     auto chdr_module = m.def_submodule("chdr", "CHDR Parsing");
     export_utils(chdr_module);
+
+    // Register property tree
+    export_property_tree(m);
 }

host/python/uhd/__init__.py

@@ -14,3 +14,6 @@ from . import rfnoc
 from . import dsp
 from . import chdr
 from .libpyuhd.paths import *
+from .property_tree import PropertyTree
+
+

host/python/uhd/property_tree.py

@@ -0,0 +1,12 @@
+#
+# Copyright 2020 Ettus Research, a National Instruments Brand
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""
+Access to the property tree
+"""
+
+from . import libpyuhd as lib
+
+PropertyTree = lib.property_tree