I try to pass a dictionary (unordered_map) structure from python to C++ through pybind11. On the python side I am trying to do:
v1 = { 1:3.0, 2:4.0} v2 = { 7:13.0, 8:14.0, 15:22.0} data={'ab':v1, 'bz':v2} cpp_run(data)
On the C++ side, I have
#include <iostream> #include <pybind11/pybind11.h> #include <pybind11/numpy.h> #include <pybind11/stl.h> namespace py = pybind11; void cpp_run(py::dict& results) { for (auto it : results) { const std::string& name = reinterpret_cast<const std::string&>(it.first); const py::dict& values = reinterpret_cast<const py::dict&>(it.second); for (auto iter : values) { const int& id = reinterpret_cast<const int&>(iter.first); const double& value = reinterpret_cast<const double&>(iter.second); std::cout << "name:" << name << ", id:" << id << ", value:" << value << std::endl; } } }
It prints garbage data. I used reinterpret_cast to satisfy the Visual Studio compiler.
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Answer
I sort of solve this by using py::cast on the C++ side:
void cpp_run(const py::dict& results) { for (auto it : results) { const std::string& name = py::cast<const std::string>(it.first); std::unordered_map<int, double>& a_map = py::cast <std::unordered_map<int, double> >(it.second); for (auto iter = a_map.begin(); iter != a_map.end(); ++iter) { of << "name:" << name << ", id:" << iter->first << ", value:" << iter->second << std::endl; } } }