微信公众号开发系列--自动回复实现天气预报查询

上次我们讲了微信公众号的部署，今天我们来实现一个小功能，自动回复天气预报的播报。

使用方法如下：在iTesting公众号里直接回复 “城市天气”，将会把上海最近的天气信息返回给你，例如输入上海天气，会返回给你上海的天气情况。

通过仔细阅读微信开发文档，我们知道：

当用户发送消息给公众号时（或某些特定的用户操作引发的事件推送时），会产生一个POST请求，开发者可以在响应包（Get）中返回特定XML结构，来对该消息进行响应（现支持回复文本、图片、图文、语音、视频、音乐）。严格来说，发送被动响应消息其实并不是一种接口，而是对微信服务器发过来消息的一次回复。

简单来说，当你输入信息要求微信服务器返回你一个信息时，是在做一个Post请求，这个post请求是text格式的，微信收到会转给你自己的服务器，你的服务器处理好后，按照微信的要求把内容返回，然后你就可以看到回复了。
原理知道了，那么如何开发？步骤如下：

首先把回复的xml准备好，放在文件里，例如 txt_message.xml.

<xml><ToUserName><![CDATA[{to_user}]]></ToUserName>
<FromUserName><![CDATA[{from_user}]]></FromUserName>
<CreateTime>{c_time}</CreateTime>
<MsgType><![CDATA[text]]></MsgType>
<Content><![CDATA[{content_value}]]></Content>
</xml>

调用天气预报API生成天气。

# -*- coding: UTF-8 -*-
import sys
reload(sys)
sys.setdefaultencoding("utf-8")
import requests
import settings
class GetWeather(object):
    headers = {'apikey': settings.baidu_apikey}
    def get_city_code(self, city):
        url = 'http://apis.baidu.com/apistore/weatherservice/citylist?cityname=%s'%city
        r = requests.get(url, headers=self.headers)
        j =  r.json()['retData']
        for i in j:
            if i['name_cn'] == city:
                return i['area_id']
    def get_weather(self, city):
        city_code = self.get_city_code(city)
        url = 'http://apis.baidu.com/apistore/weatherservice/recentweathers?cityname={}&cityid={}'.format(city, city_code)
        r = requests.get(url, headers=self.headers)
        raw_data = r.json()
        if raw_data.has_key("retData"):
            if type(raw_data['retData']) == dict:
                j = raw_data['retData']['today']
                content = "今日{city}的天气情况如下：\n" \
                          "日期：{date},"  \
                          "{week}, "  \
                          "当前温度：{curTemp}, "  \
                          "{type}, {fengxiang}, {fengli}"  \
                          "最高气温：{hightemp}, " \
                          "最低气温：{lowtemp}, " \
                          "PM值：{aqi}" .format(city=city, date=j['date'], week=j['week'], curTemp=j['curTemp'],type=j['type'],\
                                             fengxiang=j['fengxiang'], fengli=j['fengli'], hightemp=j['hightemp'],\
                                              lowtemp=j['lowtemp'], aqi=j['aqi'])
                return content
            else:
                return "您输入的城市有误，请重新输入."
        else:
            return "您输入的城市有误，请重新输入."
if __name__ == "__main__":
    w = GetWeather()
    print w.get_weather('上海')

把上述步骤里得到的返回值，嵌入到step1的变量里，返回给微信Server。具体做法:


@app.route('/',  methods=['GET', 'POST'])
def wechat():
        if request.method == 'GET':
            if len(request.args) > 0:
                temparr = []
                token = settings.token
                signature = request.args["signature"]
                timestamp = request.args["timestamp"]
                nonce = request.args["nonce"]
                echostr = request.args["echostr"]
                temparr.append(token)
                temparr.append(timestamp)
                temparr.append(nonce)
                temparr.sort()
                newstr = "".join(temparr)
                sha1str = hashlib.sha1(newstr)
                temp = sha1str.hexdigest()
                if signature == temp:
                    return make_response(echostr)
                else:
                    return make_response("Access denied")
            else:
                return make_response("Wrong args received")
        else:
            raw_data = request.stream.read()
            xml_raw = ET.fromstring(raw_data)
            msg = {}
            for child in xml_raw:
                msg[child.tag] = child.text
            msgtype = msg['MsgType']
            tou = msg['ToUserName']
            fromu = msg['FromUserName']
            time_str = str(int(time.time()))
            if msgtype == "event":
                event_msg = xml_raw.find('Event').text
                print event_msg
                if event_msg == "subscribe":
                    sub_content = settings.welcome_message
                else:
                    sub_content = "error"
                xml_reader = XMLHelper().read_xml("txt_message.xml")
                response = make_response(xml_reader.format(to_user=fromu, from_user=tou, c_time=time_str, content_value=sub_content))
            elif msgtype == "image":
                media_id = msg['MediaId']
                xml_reader = XMLHelper().read_xml("img_message.xml")
                response = make_response(xml_reader.format(to_user=fromu, from_user=tou, c_time=time_str, media_id=media_id))
            elif msgtype == "voice":
                media_id = msg['MediaId']
                xml_reader = XMLHelper().read_xml("voice_message.xml")
                response = make_response(xml_reader.format(to_user=fromu, from_user=tou, c_time=time_str, media_id=media_id))
            elif msgtype == 'text':
                # co = xml_raw.find('Content').text.strip().split(' ')
                # if co[len(co)-1] == '天气':
                #     weather = GetWeather()
                #     auto_response_content = weather.get_weather(co[:-1][0])
                # else:
                r = RobotHelper()
                auto_response_content = r.get_robot(xml_raw.find('Content').text)
                xml_reader = XMLHelper().read_xml("txt_message.xml")
                response = make_response(xml_reader.format(to_user=fromu, from_user=tou, c_time=time_str, content_value=auto_response_content))
            elif msgtype in ["video","shortvideo"]:
                title = "My video"
                description = "Check out my video"
                media_id = msg['MediaId']
                xml_reader = XMLHelper().read_xml("video_message.xml")
                response = make_response(xml_reader.format(to_user=fromu, from_user=tou, c_time=time_str, media_id=media_id, title=title, description=description))
            else:
                unknown_content = u"""我不知道你在干什么,无法回复你"""
                xml_reader = XMLHelper().read_xml("txt_message.xml")
                response = make_response(xml_reader.format(to_user=fromu, from_user=tou, c_time=time_str, content_value=unknown_content))
            response.content_type = 'application/xml'
            return response