《精通Python设计模式》学习之工厂方法

小书，在我以前作数据库的连接时，就用了这个工厂方法的。

归纳总结一下，更有利于成长吧。

import xml.etree.ElementTree as etree
import json

class JSONConnector:

    def __init__(self, filepath):
        self.data = dict()
        with open(filepath, mode='r', encoding='utf-8') as f:
            self.data = json.load(f)

    @property
    def parsed_data(self):
        return self.data

class XMLConnector:

    def __init__(self, filepath):
        self.tree = etree.parse(filepath)

    @property
    def parsed_data(self):
        return self.tree

def connection_factory(filepath):
    if filepath.endswith('json'):
        connector = JSONConnector
    elif filepath.endswith('xml'):
        connector = XMLConnector
    else:
        raise ValueError('Can not connect to {}'.format(filepath))
    return connector(filepath)

def connect_to(filepath):
    factory = None
    try:
        factory = connection_factory(filepath)
    except ValueError as ve:
        print(ve)
    return factory

def main():
    sqlite_factory = connect_to('person.sq3')

    xml_factory = connect_to('person.xml')
    xml_data = xml_factory.parsed_data
    liars = xml_data.findall(".//{}[{}='{}']".format('person',
                                                     'lastName', 'Smith'))
    print('found: {} persons'.format(len(liars)))
    for liar in liars:
        print('first name: {}'.format(liar.find('firstName').text))
        print('last name: {}'.format(liar.find('lastName').text))

    json_factory = connect_to('donut.json')
    json_data = json_factory.parsed_data
    print('found: {} donuts'.format(len(json_data)))
    for donut in json_data:
        print('name: {}'.format(donut['name']))
        print('price: ${}'.format(donut['ppu']))

if __name__ == '__main__':
    main()