Hi,

Please try the following code.

@http.route('/stock', auth='user')
def stock(self, **kw):
    product = request.env['product.template'].search([('id', '=', kw['product_id'])])
    warehouse = request.env['stock.warehouse'].search([])
    stock = []
    for variant in products.product_variant_ids:
        """Looping through the product variants"""
        wh_qty = {}
        for j in warehouse:
            wh_qty[j.name] = variant.with_context(
                {'warehouse': j.id}).qty_available
            """Getting the qty from the current warehouse"""
        item = {
            'size': variant.attribute_value_ids.name,
            'total': variant.qty_available,
        }
        for k in wh_qty:
            item[k] = wh_qty[k]
        stock.append(item)
    return Response(json.dumps(stock))