import parse
from decimal import Decimal
import delorean


class PriceLog(object):

    def __init__(self, timestamp, product_id, price):
        self.timestamp = timestamp
        self.product_id = product_id
        self.price = price

    def __repr__(self):
        return '<PriceLog ({}, {}, {})>'.format(self.timestamp,
                                                self.product_id,
                                                self.price)

    @classmethod
    def parse(cls, text_log):
        '''
        Parse from a text log with the format
        [<Timestamp>] - SALE - PRODUCT: <product id> - PRICE: $<price>
        to a PriceLog object
        '''
        def price(string):
            return Decimal(string)

        def isodate(string):
            return delorean.parse(string)

        FORMAT = ('[{timestamp:isodate}] - SALE - PRODUCT: {product:d} - '
                  'PRICE: ${price:price}')

        formats = {'price': price, 'isodate': isodate}
        result = parse.parse(FORMAT, text_log, formats)

        return cls(timestamp=result['timestamp'],
                   product_id=result['product'],
                   price=result['price'])

執行結果如下：

>>> log = '[2018-05-05T11:07:12.267897] - SALE - PRODUCT: 1345 - PRICE: $09.99'

>>> PriceLog.parse(log)

<PriceLog (Delorean(datetime=datetime.datetime(2018, 5, 5, 11, 7, 12, 267897), timezone='UTC'), 1345, 9.99)>