python: Add find() to the Python API

This a mapping of uhd::device::find() into uhd.find() on the Python
side. The uhd::device is intentionally not mapped into Python (prefer
MultiUSRP or RfnocGraph instead), so the namespace is moved up one
level.

Example:
>>> import uhd
>>> # Now print the device args for all found B200s:
>>> for dev_args in uhd.find("type=b200")): print(dev_args.to_string())

host/lib/device_python.cpp

@@ -0,0 +1,19 @@
+//
+// Copyright 2020 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#include <pybind11/complex.h>
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+
+namespace py = pybind11;
+
+#include "device_python.hpp"
+#include <uhd/device.hpp>
+
+void export_device(py::module& m)
+{
+    m.def("find", [](const uhd::device_addr_t& hint) { return uhd::device::find(hint); });
+}

host/lib/device_python.hpp

@@ -0,0 +1,9 @@
+//
+// Copyright 2020 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#pragma once
+
+void export_device(py::module& m);

host/python/CMakeLists.txt

@@ -32,6 +32,7 @@ execute_process(
 add_library(pyuhd SHARED
     pyuhd.cpp
     ${CMAKE_SOURCE_DIR}/lib/property_tree_python.cpp
+    ${CMAKE_SOURCE_DIR}/lib/device_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 "device_python.hpp"
 #include "property_tree_python.hpp"
 #include "rfnoc/ddc_block_control_python.hpp"
 #include "rfnoc/duc_block_control_python.hpp"
@@ -61,6 +62,9 @@ PYBIND11_MODULE(libpyuhd, m)
     // (otherwise we will see segmentation faults)
     init_numpy();
 
+    // Register uhd::device::find
+    export_device(m);
+
     // Register paths submodule
     auto paths_module = m.def_submodule("paths", "Path Utilities");
     export_paths(paths_module);

host/python/uhd/__init__.py

@@ -14,6 +14,7 @@ from . import rfnoc
 from . import dsp
 from . import chdr
 from .libpyuhd.paths import *
+from .libpyuhd import find
 from .property_tree import PropertyTree