static IntPtr py_import;

static CLRModule root;

static MethodWrapper hook;

//===================================================================

// Initialization performed on startup of the Python runtime.

//===================================================================

internal static void Initialize() {

// Initialize the Python <--> CLR module hook. We replace the

// built-in Python __import__ with our own. This isn't ideal,

// but it provides the most "Pythonic" way of dealing with CLR

// modules (Python doesn't provide a way to emulate packages).

IntPtr dict = Runtime.PyImport_GetModuleDict();

IntPtr mod = Runtime.PyDict_GetItemString(dict, "__builtin__");

py_import = Runtime.PyObject_GetAttrString(mod, "__import__");

hook = new MethodWrapper(typeof(ImportHook), "__import__");

Runtime.PyObject_SetAttrString(mod, "__import__", hook.ptr);

Runtime.Decref(hook.ptr);

root = new CLRModule();

Runtime.Incref(root.pyHandle); // we are using the module two times

Runtime.PyDict_SetItemString(dict, "CLR", root.pyHandle);

Runtime.PyDict_SetItemString(dict, "clr", root.pyHandle);

}

//===================================================================

// Cleanup resources upon shutdown of the Python runtime.

//===================================================================

internal static void Shutdown() {

Runtime.Decref(root.pyHandle);

Runtime.Decref(root.pyHandle);

Runtime.Decref(py_import);

}

//===================================================================

// The actual import hook that ties Python to the managed world.

//===================================================================

public static IntPtr __import__(IntPtr self, IntPtr args, IntPtr kw) {

// Replacement for the builtin __import__. The original import

// hook is saved as this.py_import. This version handles CLR

// import and defers to the normal builtin for everything else.

int num_args = Runtime.PyTuple_Size(args);

if (num_args < 1) {

return Exceptions.RaiseTypeError(

"__import__() takes at least 1 argument (0 given)"

);

}

// borrowed reference

IntPtr py_mod_name = Runtime.PyTuple_GetItem(args, 0);

if ((py_mod_name == IntPtr.Zero) ||

(!Runtime.IsStringType(py_mod_name))) {

return Exceptions.RaiseTypeError("string expected");

}

// Check whether the import is of the form 'from x import y'.

// This determines whether we return the head or tail module.

IntPtr fromList = IntPtr.Zero;

bool fromlist = false;

if (num_args >= 4) {

fromList = Runtime.PyTuple_GetItem(args, 3);

if ((fromList != IntPtr.Zero) &&

(Runtime.PyObject_IsTrue(fromList) == 1)) {

fromlist = true;

}

}

string mod_name = Runtime.GetManagedString(py_mod_name);

// Check these BEFORE the built-in import runs; may as well

// do the Incref()ed return here, since we've already found

// the module.

if (mod_name == "clr") {

root.InitializePreload();

Runtime.Incref(root.pyHandle);

return root.pyHandle;

}

if (mod_name == "CLR") {

Exceptions.deprecation("The CLR module is deprecated. " +

"Please use 'clr'.");

root.InitializePreload();

Runtime.Incref(root.pyHandle);

return root.pyHandle;

}

string realname = mod_name;

if (mod_name.StartsWith("CLR.")) {

realname = mod_name.Substring(4);

string msg = String.Format("Importing from the CLR.* namespace "+

"is deprecated. Please import '{0}' directly.", realname);

Exceptions.deprecation(msg);

}

else {

// 2010-08-15: Always seemed smart to let python try first...

// This shaves off a few tenths of a second on test_module.py

// and works around a quirk where 'sys' is found by the

// LoadImplicit() deprecation logic.

// Turns out that the AssemblyManager.ResolveHandler() checks to see if any

// Assembly's FullName.ToLower().StartsWith(name.ToLower()), which makes very

// little sense to me.

IntPtr res = Runtime.PyObject_Call(py_import, args, kw);

if (res != IntPtr.Zero) {

// There was no error.

return res;

}

// There was an error

if (!Exceptions.ExceptionMatches(Exceptions.ImportError)) {

// and it was NOT an ImportError; bail out here.

return IntPtr.Zero;

}

// Otherwise, just clear the it.

Exceptions.Clear();

}

string[] names = realname.Split('.');

// Now we need to decide if the name refers to a CLR module,

// and may have to do an implicit load (for b/w compatibility)

// using the AssemblyManager. The assembly manager tries

// really hard not to use Python objects or APIs, because

// parts of it can run recursively and on strange threads.

//

// It does need an opportunity from time to time to check to

// see if sys.path has changed, in a context that is safe. Here

// we know we have the GIL, so we'll let it update if needed.

AssemblyManager.UpdatePath();

if (!AssemblyManager.IsValidNamespace(realname)) {

if (!AssemblyManager.LoadImplicit(realname))

{

// May be called when a module being imported imports a module.

// In particular, I've seen decimal import copy import org.python.core

return Runtime.PyObject_Call(py_import, args, kw);

}

}

// See if sys.modules for this interpreter already has the

// requested module. If so, just return the exising module.

IntPtr modules = Runtime.PyImport_GetModuleDict();

IntPtr module = Runtime.PyDict_GetItem(modules, py_mod_name);

if (module != IntPtr.Zero) {

if (fromlist) {

Runtime.Incref(module);

return module;

}

module = Runtime.PyDict_GetItemString(modules, names[0]);

Runtime.Incref(module);

return module;

}

Exceptions.Clear();

// Traverse the qualified module name to get the named module

// and place references in sys.modules as we go. Note that if

// we are running in interactive mode we pre-load the names in

// each module, which is often useful for introspection. If we

// are not interactive, we stick to just-in-time creation of

// objects at lookup time, which is much more efficient.

// NEW: The clr got a new module variable preload. You can

// enable preloading in a non-interactive python processing by

// setting clr.preload = True

ModuleObject head = (mod_name == realname) ? null : root;

ModuleObject tail = root;

root.InitializePreload();

for (int i = 0; i < names.Length; i++) {

string name = names[i];

ManagedType mt = tail.GetAttribute(name, true);

if (!(mt is ModuleObject)) {

string error = String.Format("No module named {0}", name);

Exceptions.SetError(Exceptions.ImportError, error);

return IntPtr.Zero;

}

if (head == null) {

head = (ModuleObject)mt;

}

tail = (ModuleObject) mt;

if (CLRModule.preload) {

tail.LoadNames();

}

Runtime.PyDict_SetItemString(modules, tail.moduleName,

tail.pyHandle

);

}

ModuleObject mod = fromlist ? tail : head;

if (fromlist && Runtime.PySequence_Size(fromList) == 1) {

IntPtr fp = Runtime.PySequence_GetItem(fromList, 0);

if ((!CLRModule.preload) && Runtime.GetManagedString(fp) == "*") {

mod.LoadNames();

}

Runtime.Decref(fp);

}

Runtime.Incref(mod.pyHandle);

return mod.pyHandle;

}