Using __setattr__ & __getattr__ with properties

Question

I'm attempting to write a more pythonic interaction with win32com.client for my own use so I can do things like:

with Presentation(close=True) as P:
        table = P[0].tables[0]
        table.cells.Shape.TextFrame.TextRange.Text= 'hello'

I've managed to get the above working (very satisfying) by overloading __getattr__ and __setattr__.

I want to interact with a powerpoint table as an array not a linear object so I created the CellRange object

This is from tables.py, which handles the array views of win32com.client tables.

from itertools import product
import numpy as np
from win32com.client import pywintypes

ALIGN_LABELS = 'bottom bottom_base middle top top_base mixed'.split()
ALIGN_LABELS_N = {k: i for i, k in enumerate(ALIGN_LABELS)}

class Win32Interface(object):
    def __init__(self, win32_object):
        super(Win32Interface, self).__setattr__('win32_object', win32_object)

    def __setattr__(self, k, v):
        setattr(self.win32_object, k, v)

    def __getattr__(self, v):
        return getattr(self.win32_object, v)


class Cell(Win32Interface):
    def __repr__(self):
        return self.Shape.TextFrame.TextRange.Text

    @property
    def text(self):
        return self.Shape.TextFrame.TextRange.Text

    @text.setter
    def text(self, v):
        setattr(self.Shape.TextFrame.TextRange, 'Text', v)


class CellRange(object):
    def __init__(self, cell_array):
        super(CellRange, self).__init__()
        super(CellRange, self).__setattr__('cell_array', cell_array)

    def _apply_map(self, f):
        func = np.vectorize(f)
        return func(self.cell_array)

    def __getattr__(self, k):
        try:
            arr = self._apply_map(lambda x: getattr(x, k))
            return CellRange(arr)
        except (AttributeError, pywintypes.com_error):
            return getattr(self.cell_array, k)

    def __setattr__(self, k, v):
        if hasattr(v, 'shape'):
            assert self.shape == v.shape, 'mismatched shape'
            for cell, value in zip(self.cell_array.ravel(), v.ravel()):
                cell.__setattr__(k, value)
        else:
            self._apply_map(lambda x: setattr(x, k, v))

    def __repr__(self):
        return self.cell_array.__repr__()

Ignoring the Table object for the moment, I want to know why

cell_range = CellRange(cell_array)
    cell_range.text = 'hello'

throws up a cannot be set error. The above calls __setattr__ which then calls _apply_map to set each element of the array, this calls Cell.__setattr__. Why can I do print cell_range.text but not cell_range.text = 'hello'?

Answer 1

Stumbled into the solution about 10 minutes after I posted!

The answer is to use Object's __setattr__ instead of Win32Interface's

So obvious!

class Win32Interface(object):
    def __init__(self, win32_object):
        super(Win32Interface, self).__setattr__('win32_object', win32_object)

    def __setattr__(self, k, v):
        if k in self.properties:
            super(Win32Interface, self).__setattr__(k, v)
        else:
            setattr(self.win32_object, k, v)

    def __getattr__(self, v):
        return getattr(self.win32_object, v)

    @property
    def properties(self):
        class_items = self.__class__.__dict__.iteritems()
        return {k:v for k, v in class_items if isinstance(v, property) and k != 'properties'}