Can you try to following command to get the size in bytes of the wchar_t type?

>>> import types
>>> ctypes.sizeof(ctypes.c_wchar)
4

You can also use _PyObject_Dump() to dump your string:

>>> import ctypes
>>> x="abc"
>>> _PyObject_Dump=ctypes.pythonapi._PyObject_Dump
>>> _PyObject_Dump.argtypes=(ctypes.py_object,)
>>> _PyObject_Dump(x)
object  : 'abc'
type    : str
refcount: 5
address : 0xb70bf980
48

Then you can use _PyObject_Dump() on your string.

You may also try: print(list(dirname)).

It's really strange that something very common like string concatenation returns an invalid string.