def _update_stocks(symbols):
"""
Update models.Stock entities.
:param symbols: Iterable of stock symbols to update.
:return: dict mapping symbols to new prices, dict mapping symbols to (old price, new price) for changed symbols.
"""
to_put = []
symbol_price_updated_dict = {}
if symbols is None:
stocks_ = list(Stock.query())
symbols = [s.key.id() for s in stocks_]
else:
stocks_ = [Stock.get_by_id(s) for s in symbols]
symbol_price_dict = stocks.get_stock_prices(symbols)
for stock in stocks_:
if stock is None:
continue
symbol = stock.key.id()
price = symbol_price_dict.get(symbol, None)
if stock.price != price:
symbol_price_updated_dict[symbol] = (stock.price, price)
stock.price = price
to_put.append(stock)
ndb.put_multi(to_put)
return symbol_price_dict, symbol_price_updated_dict
