Understanding the code

The following is the code that we are going to be looking at in this chapter:

from datetime import datetime

from .stock import Stock
from .rule import PriceRule

class AlertProcessor:
    def __init__(self):
        self.exchange = {"GOOG": Stock("GOOG"), "AAPL": Stock("AAPL")}
        rule_1 = PriceRule("GOOG", lambda stock: stock.price > 10)
        rule_2 = PriceRule("AAPL", lambda stock: stock.price > 5)
        self.exchange["GOOG"].updated.connect(
            lambda stock: print(stock.symbol, stock.price) \
                if rule_1.matches(self.exchange) else None)
        self.exchange["AAPL"].updated.connect(
            lambda stock: print(stock.symbol, stock.price) \
                if rule_2.matches(self.exchange) else None)

        updates = []
        with open("updates.csv", "r") as fp:
            for line in fp.readlines():
                symbol, timestamp, price = line.split(",")
                updates.append((symbol, datetime.strptime(timestamp...