Add an __init__.py file so we can add paths to CUDA libs on windows.

setup.py

@@ -229,13 +229,14 @@ setup(
     author_email='davis@dlib.net',
     url='https://github.com/davisking/dlib',
     license='Boost Software License',
-    ext_modules=[CMakeExtension('dlib','tools/python')],
+    ext_modules=[CMakeExtension('_dlib_pybind11','tools/python')],
     cmdclass=dict(build_ext=CMakeBuild, test=PyTest),
     zip_safe=False,
     # We need an older more-itertools version because v6 broke pytest (for everyone, not just dlib)
     tests_require=['pytest==3.8', 'more-itertools<6.0.0'],
     #install_requires=['cmake'], # removed because the pip cmake package is busted, maybe someday it will be usable.
     packages=['dlib'],
+    package_dir={'': 'tools/python'},
     keywords=['dlib', 'Computer Vision', 'Machine Learning'],
     classifiers=[
         'Development Status :: 5 - Production/Stable',

tools/python/CMakeLists.txt

@@ -68,8 +68,6 @@ if(NOT ${DLIB_NO_GUI_SUPPORT})
    list(APPEND python_srcs src/gui.cpp)
 endif()
 
-pybind11_add_module(dlib_python ${python_srcs})
-target_link_libraries(dlib_python PRIVATE dlib::dlib)
-# Set the output library name to dlib because that's what setup.py and distutils expects.
-set_target_properties(dlib_python PROPERTIES OUTPUT_NAME dlib)
+pybind11_add_module(_dlib_pybind11 ${python_srcs})
+target_link_libraries(_dlib_pybind11 PRIVATE dlib::dlib)
 

tools/python/dlib/__init__.py

+from _dlib_pybind11 import *
+from _dlib_pybind11 import __version__, __time_compiled__
+
+
+try:
+    import os
+    # On windows you must call os.add_dll_directory() to allow linking to external DLLs.  See
+    # https://docs.python.org/3.8/whatsnew/3.8.html#bpo-36085-whatsnew.
+    os.add_dll_directory(os.path.join(os.environ['CUDA_PATH'], 'bin'))
+except (AttributeError,KeyError):
+    pass

tools/python/src/dlib.cpp

@@ -37,7 +37,7 @@ void bind_line(py::module& m);
 void bind_gui(py::module& m);
 #endif
 
-PYBIND11_MODULE(dlib, m)
+PYBIND11_MODULE(_dlib_pybind11, m)
 {
     warn_about_unavailable_but_used_cpu_instructions();