How to expose an object function done in C++

Helper

On 15/07/2016 at 07:13, xxxxxxxx wrote:

Hi!

Sorry for the late reply. It's possible to define new Python functions using the library defined in c4d_libs/lib_py.h
This library definitions are not documented currenly and many are meant for internal use only.

To expose a Python function a new module has to be initialized with PythonLibrary::InitModule().
Here is some code:

// Global table of c4d.extendpyapi functions for PythonLibrary::InitModule()
static maxon::BaseArray<PythonMethodData>* g_extendpyapi_functions = nullptr;
  
// Prints "Hello from Python!" to the console
static _PyObject *extendpyapi_HelloPython(_PyObject *self)
{
  PythonLibrary pylib;
  GePrint("Hello from Python!");
  return pylib.ReturnPyNone();
}
  
// Initializes c4d.extendpyapi module
void InitExtendPython()
{
  PythonLibrary pylib;
  
  // Allocates c4d.extendpyapi module functions
  g_extendpyapi_functions = NewObjClear(maxon::BaseArray<PythonMethodData>);
  if (g_extendpyapi_functions == nullptr)
    return;
  
  // Initializes c4d.extendpyapi module functions
  g_extendpyapi_functions->Resize(2);
  PythonMethodData* moduleFunctions = g_extendpyapi_functions->GetFirst();
  moduleFunctions[0].Init("HelloPython", (PyFn)extendpyapi_HelloPython, PYFN_FLAGS_NOARGS, "HelloPython() - Extend Python API");
  moduleFunctions[1].Init(String(), nullptr, PYFN_FLAGS_0, String()); // Last dummy element!
  
  // Initializes c4d.extendpyapi module
  if (pylib.InitModule("c4d.extendpyapi", moduleFunctions, "Extend Python API"))
    GePrint("\'c4d.extendpyapi\' module successfully initialized");
}
 
// Frees the module global function table
void FreeExtendPython()
{
  DeleteObj(g_extendpyapi_functions);
}

InitExtendPython()/FreeExtendPython() have to called from within PluginMessage() C4DPL_PYINITTYPES/C4DPL_PYFINALIZE:

Bool PluginMessage(Int32 id, void* data)
{
  case C4DPL_PYINITTYPES:
  {
    InitExtendPython();
    return true;
  }
  case C4DPL_PYFINALIZE:
  {
    FreeExtendPython();
    return true;
  }
  
  return false;
}

To pass basic parameters like string, integer or float use PythonLibrary::ParseTupleAndKeywords() like shown in the following code snippet:

static _PyObject *extendpyapi_PassParameters(_PyObject *self, _PyObject *args, _PyObject *keywords)
{
  PythonLibrary pylib;
 
  String str;
  Int32 integer = 0;
  Float real = 0.0f;
  
  const Char *kwlist[] = {"str", "integer", "real", nullptr};
  if (!pylib.ParseTupleAndKeywords(args, keywords, "$if", kwlist, &str, &integer, &real))
    return nullptr;
  
  if (str.Content())
    GePrint("Parameter str: " + str);
  
  GePrint("Parameter integer: " + String::IntToString(integer));
  GePrint("Parameter real: " + String::FloatToString(real));
 
  return pylib.ReturnPyNone();
}

If a function accepts parameters pass PYFN_FLAGS_KEYWORDS instead of PYFN_FLAGS_NOARGS for the Init() call.

Finally, to parse a GeData/baselist object use 'G' format:

static _PyObject *extendpyapi_PassBaseList(_PyObject *self, _PyObject *args, _PyObject *keywords)
{
  PythonLibrary pylib;
 
  GeData data;
 
  const Char *kwlist[] = {"baselist", nullptr};
  if (!pylib.ParseTupleAndKeywords(args, keywords, "G", kwlist, &data))
    return nullptr;
 
  if (data.GetType() == DA_ALIASLINK)
  {
    BaseLink* link = data.GetBaseLink();
    if (link == nullptr)
      return pylib.ReturnPyNone();
 
    BaseList2D* baseList = link->GetLink(nullptr);
    if (baseList == nullptr)
      return pylib.ReturnPyNone();
 
    GePrint("Passed baselist: " + baseList->GetName());
  }
 
  return pylib.ReturnPyNone();
}

Helper

On 15/07/2016 at 10:15, xxxxxxxx wrote:

Howdy,

Wow, thanks Yannick!

I've been working on making aspects of my plugins scriptable through cofffee and wanted to included python scriptability, too. This gives me a place to start.

Adios,
Cactus Dan

Helper

On 28/07/2016 at 16:15, xxxxxxxx wrote:

Howdy,

OK, I got the passing a BaseList as a prameter with the "G" format, but suppose I want to pass both a BaseList and an interger or real in the same function? How would that be formatted?

Adios,
Cactus Dan

Helper

On 29/07/2016 at 02:37, xxxxxxxx wrote:

Originally posted by xxxxxxxx

OK, I got the passing a BaseList as a prameter with the "G" format, but suppose I want to pass both a BaseList and an interger or real in the same function? How would that be formatted?

Like the argument parsing in the function example extendpyapi_PassParameters() I posted above, concatenate the characters for each parameter.
For instance:

GeData data;
Int32 integer = 0;
Float real = 0.0f;
  
const Char *kwlist[] = {"baselist", "integer", "real", nullptr};
if (!pylib.ParseTupleAndKeywords(args, keywords, "Gif", kwlist, &data, &integer, &real))
    return nullptr;

Helper

On 29/07/2016 at 04:53, xxxxxxxx wrote:

Howdy,

DOH! It's the strings that always throw me off when they're used for anything other than printing.
But I get it now:
"$" = string format
"i" = integer format
"f" = float format
"G" = GeData format

Possibly if the example had the float first like "$fi" then I might have been able to figure that out. But, with it the other way around, no matter how many times I looked at it, I still saw the word "if", and got confused.

Thanks for the clarification.

Adios,
Cactus Dan

Helper

On 29/07/2016 at 05:53, xxxxxxxx wrote:

You're welcome

"C" can also be used to parse BaseContainer* too (note only pointer to BaseContainer, initialize with nullptr before calling ParseTupleAndKeywords()).

Helper

On 29/07/2016 at 06:07, xxxxxxxx wrote:

Howdy,

Thanks. Is there a complete list of formatting letters that you could post?

Also, is there a way to add global symbols in python like in coffee, and if so, can you post an example?

Adios,
Cactus Dan

Helper

On 26/04/2017 at 00:05, xxxxxxxx wrote:

Hello,

I know this is a bit older topic but the last question from Cactus Dan was not answered and I also need it. Especially I need to transfer BaseObject to and from python script.

So again, we just need a table of all formatting letters and types that Cinema python binding API uses.

Just for completeness, python build-in formatting letters seems to work and are available here: https://docs.python.org/2.7/c-api/arg.html?highlight=parsetupleandkeywords#c.PyArg_ParseTupleAndKeywords

Helper

On 26/04/2017 at 02:38, xxxxxxxx wrote:

Hi Miro,

Originally posted by xxxxxxxx

I know this is a bit older topic but the last question from Cactus Dan was not answered and I also need it. Especially I need to transfer BaseObject to and from python script.

To parse a BaseList based object, use 'G' format character as show in my above code snippet's function extendpyapi_PassBaseList(). The object can be casted to the most interesting type after retrieving it.

Originally posted by xxxxxxxx

So again, we just need a table of all formatting letters and types that Cinema python binding API uses.

PythonLibrary::ParseTupleAndKeywords() accepts the following format characters for Cinema 4D C++ API classes:
- $: String
- %: Filename
- M: Matrix
- V: Vector
- Q: Quaternion
- BaseContainer*
- G: GeData (versatile: can parse a BaseList, a custom data, a time, etc.)
- T: BaseTime
- X: BaseThread

Originally posted by xxxxxxxx

Just for completeness, python build-in formatting letters seems to work and are available here: https://docs.python.org/2.7/c-api/arg.html?highlight=parsetupleandkeywords#c.PyArg_ParseTupleAndKeywords

PythonLibrary::ParseTupleAndKeywords()also accepts the following standard format characters: b, B, j, h, i, I, v, l, L, r, f, d, c

Helper

On 27/04/2017 at 23:34, xxxxxxxx wrote:

That's perfect! Thank you.

Helper

On 24/09/2017 at 13:07, xxxxxxxx wrote:

Hello all,

It seems to be that i's only possible to make a python extension library as a plugin. Which plugin then is best suited? A command plugin, I would guess, or is there another plugin that loads completely automatic at startup?

I need something that is always available, so that I don't have to think about loading the library. Much like the c++ example here: page_creating_libraries.html

Regards,

Hermen

Helper

On 25/09/2017 at 01:29, xxxxxxxx wrote:

Hello,

a "_ plugin_" is just a custom module loaded by Cinema. So a "plugin" does not need to include anything e.g. a command data extension. You only have to implement PluginStart()/PluginMessage()/PluginEnd(), see Plugin Functions Manual. In such a PluginMessage () function you have to register your Python extension as shown above.

best wishes,
Sebastian

Helper

On 25/09/2017 at 02:53, xxxxxxxx wrote:

Aha!
Now I understand, thanks for clearing that up!

regards,

Hermen