虽然结果是正确的，但感觉教程写的这么简单，为何练习刚开始做，就觉得无从下手呢……

class SaxWeatherHandler(object):

def __init__(self):
    self.CurrentData = ""
    self.city = ""
    self.forecast = []
def start_element(self, name, attrs):
    if name == "yweather:location":
        self.city = attrs["city"]
    if name == "yweather:forecast":
        date = attrs["date"]
        high = attrs["high"]
        low = attrs["low"]
        weatherdate = {'date':date, 'high':high, 'low':low}
        self.forecast.append(weatherdate)

def end_element(self, name):
    pass

def char_data(self, text):
    pass

def parseXml(xml_str):

print(xml_str)

handler = SaxWeatherHandler()
parser = ParserCreate()
parser.StartElementHandler = handler.start_element
parser.EndElementHandler = handler.end_element
parser.CharacterDataHandler = handler.char_data
parser.Parse(xml_str)
return {
        'city':handler.city,
        'forecast':handler.forecast
        }