Add casting operators between py::str / py::bytes

example/example-python-types.cpp

@@ -139,6 +139,22 @@ public:
         throw std::runtime_error("This exception was intentionally thrown.");
     }
 
+    py::bytes get_bytes_from_string() {
+        return std::string("foo");
+    }
+
+    py::bytes get_bytes_from_str() {
+        return py::str(std::string("bar"));
+    }
+
+    py::str get_str_from_string() {
+        return std::string("baz");
+    }
+
+    py::str get_str_from_bytes() {
+        return py::bytes(std::string("boo"));
+    }
+
     static int value;
     static const int value2;
 };
@@ -167,6 +183,10 @@ void init_ex_python_types(py::module &m) {
         .def("pair_passthrough", &ExamplePythonTypes::pair_passthrough, "Return a pair in reversed order")
         .def("tuple_passthrough", &ExamplePythonTypes::tuple_passthrough, "Return a triple in reversed order")
         .def("throw_exception", &ExamplePythonTypes::throw_exception, "Throw an exception")
+        .def("get_bytes_from_string", &ExamplePythonTypes::get_bytes_from_string, "py::bytes from std::string")
+        .def("get_bytes_from_str", &ExamplePythonTypes::get_bytes_from_str, "py::bytes from py::str")
+        .def("get_str_from_string", &ExamplePythonTypes::get_str_from_string, "py::str from std::string")
+        .def("get_str_from_bytes", &ExamplePythonTypes::get_str_from_bytes, "py::str from py::bytes")
         .def_static("new_instance", &ExamplePythonTypes::new_instance, "Return an instance")
         .def_readwrite_static("value", &ExamplePythonTypes::value, "Static value member")
         .def_readonly_static("value2", &ExamplePythonTypes::value2, "Static value member (readonly)")

example/example-python-types.py

@@ -72,3 +72,8 @@ cstats = ConstructorStats.get(ExamplePythonTypes)
 print("Instances not destroyed:", cstats.alive())
 instance = None
 print("Instances not destroyed:", cstats.alive())
+
+print(instance.get_bytes_from_string().decode())
+print(instance.get_bytes_from_str().decode())
+print(instance.get_str_from_string())
+print(instance.get_str_from_bytes())

example/example-python-types.ref

@@ -138,3 +138,8 @@ __module__(example.ExamplePythonTypes.get_set) = example
 Instances not destroyed: 1
 ### ExamplePythonTypes @ 0x1045b80 destroyed
 Instances not destroyed: 0
+Destructing ExamplePythonTypes
+foo
+bar
+baz
+boo

include/pybind11/pytypes.h

@@ -339,6 +339,8 @@ inline iterator handle::begin() const { return iterator(PyObject_GetIter(ptr()),
 inline iterator handle::end() const { return iterator(nullptr, false); }
 inline detail::args_proxy handle::operator*() const { return detail::args_proxy(*this); }
 
+class bytes;
+
 class str : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(str, object, detail::PyUnicode_Check_Permissive)
@@ -367,6 +369,8 @@ public:
             pybind11_fail("Unable to extract string contents! (invalid type)");
         return std::string(buffer, (size_t) length);
     }
+
+    operator bytes() const;
 };
 
 inline pybind11::str handle::str() const {
@@ -395,8 +399,18 @@ public:
             pybind11_fail("Unable to extract bytes contents!");
         return std::string(buffer, (size_t) length);
     }
+
+    operator pybind11::str() const;
 };
 
+inline str::operator bytes() const {
+    return bytes((std::string) *this);
+}
+
+inline bytes::operator pybind11::str() const {
+    return pybind11::str((std::string) *this);
+}
+
 class none : public object {
 public:
     PYBIND11_OBJECT(none, object, detail::PyNone_Check)