def array2vtkCellArray(num_array, vtk_array=None):
    """Given a nested Python list or a numpy array, this method
    creates a vtkCellArray instance and returns it.

    A variety of input arguments are supported as described in the
    Parameter documentation.  If numpy arrays are given, this method
    is highly efficient.  This function is most efficient if the
    passed numpy arrays have a typecode `ID_TYPE_CODE`.  Otherwise a
    typecast is necessary and this involves an extra copy.  This
    method *always copies* the input data.

    An alternative and more efficient way to build the connectivity
    list is to create a vtkIdTypeArray having data of the form
    (npts,p0,p1,...p(npts-1), repeated for each cell) and then call
    <vtkCellArray_instance>.SetCells(n_cell, id_list).

    Parameters
    ----------

    - num_array : numpy array or Python list/tuple

      Valid values are:

        1. A Python list of 1D lists.  Each 1D list can contain one
           cell connectivity list.  This is very slow and is to be
           used only when efficiency is of no consequence.

        2. A 2D numpy array with the cell connectivity list.

        3. A Python list of 2D numpy arrays.  Each numeric array can
           have a different shape.  This makes it easy to generate a
           cell array having cells of different kinds.

    - vtk_array : `vtkCellArray` (default: `None`)

      If an optional `vtkCellArray` instance, is passed as an argument
      then a new array is not created and returned.  The passed array
      is itself modified and returned.

    Example
    -------

       >>> a = [[0], [1, 2], [3, 4, 5], [6, 7, 8, 9]]
       >>> cells = array_handler.array2vtkCellArray(a)
       >>> a = numpy.array([[0,1,2], [3,4,5], [6,7,8]], 'l')
       >>> cells = array_handler.array2vtkCellArray(a)
       >>> l_a = [a[:,:1], a[:2,:2], a]
       >>> cells = array_handler.array2vtkCellArray(l_a)

    """
    if vtk_array:
        cells = vtk_array
    else:
        cells = vtk.vtkCellArray()
    assert cells.GetClassName() == 'vtkCellArray', \
           'Second argument must be a `vtkCellArray` instance.'

    if len(num_array) == 0:
        return cells

    ########################################
    # Internal functions.
    def _slow_array2cells(z, cells):
        cells.Reset()
        vtk_ids = vtk.vtkIdList()
        for i in z:
            vtk_ids.Reset()
            for j in i:
                vtk_ids.InsertNextId(j)
            cells.InsertNextCell(vtk_ids)

    def _get_tmp_array(arr):
        try:
            tmp_arr = numpy.asarray(arr, ID_TYPE_CODE)
        except __HOLE__:
            tmp_arr = arr.astype(ID_TYPE_CODE)
        return tmp_arr

    def _set_cells(cells, n_cells, id_typ_arr):
        vtk_arr = vtk.vtkIdTypeArray()
        array2vtk(id_typ_arr, vtk_arr)
        cells.SetCells(n_cells, vtk_arr)
    ########################################

    msg = "Invalid argument.  Valid types are a Python list of lists,"\
          " a Python list of numpy arrays, or a numpy array."

    if issubclass(type(num_array), (list, tuple)):
        assert len(num_array[0]) > 0, "Input array must be 2D."
        tp = type(num_array[0])
        if issubclass(tp, list): # Pure Python list.
            _slow_array2cells(num_array, cells)
            return cells
        elif issubclass(tp, numpy.ndarray):  # List of arrays.
            # Check shape of array and find total size.
            tot_size = 0
            n_cells = 0
            for arr in num_array:
                assert len(arr.shape) == 2, "Each array must be 2D"
                shp = arr.shape
                tot_size += shp[0]*(shp[1] + 1)
                n_cells += shp[0]
            # Create an empty array.
            id_typ_arr = numpy.empty((tot_size,), ID_TYPE_CODE)
            # Now populate it with the ids.
            count = 0
            for arr in num_array:
                tmp_arr = _get_tmp_array(arr)
                shp = arr.shape
                sz = shp[0]*(shp[1] + 1)
                set_id_type_array(tmp_arr, id_typ_arr[count:count+sz])
                count += sz
            # Now set them cells.
            _set_cells(cells, n_cells, id_typ_arr)
            return cells
        else:
            raise TypeError(msg)
    elif issubclass(type(num_array), numpy.ndarray):
        assert len(num_array.shape) == 2, "Input array must be 2D."
        tmp_arr = _get_tmp_array(num_array)
        shp = tmp_arr.shape
        id_typ_arr = numpy.empty((shp[0]*(shp[1] + 1),), ID_TYPE_CODE)
        set_id_type_array(tmp_arr, id_typ_arr)
        _set_cells(cells, shp[0], id_typ_arr)
        return cells
    else:
        raise TypeError(msg)
dataset/ETHPy150Open enthought/mayavi/tvtk/array_handler.py/array2vtkCellArray