python3.5爬虫实例：根据城市名称来获取该城市最近七天的天气预报

#抓取天气网站最近7天的天气情况，写入文件并在控制台显示from bs4 import BeautifulSoup   #用来代替正则表达式取源码中相应标签的内容import randomimport requests #用来抓取网页的html源代码import socket #用做异常处理import timeimport http.client #用做异常处理import csvdef get_html(url,data=None):    """    模拟浏览器来获取网页的html代码    """    header={        'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',        'Accept-Encoding': 'gzip, deflate, sdch',        'Accept-Language': 'zh-CN,zh;q=0.8',        'Connection': 'keep-alive',        'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.235'    }    #设定超时时间，取随机数是因为防止被网站认为是爬虫    timeout=random.choice(range(80,180))    while True:        try:            rep=requests.get(url,headers=header,timeout=timeout)            rep.encoding="utf-8"            break        except socket.timeout as e:            print("3:",e)            time.sleep(random.choice(range(8,15)))        except socket.error as e:            print("4:",e)            time.sleep(random.choice(range(20,60)))        except http.client.BadStatusLine as e:            print("5:",e)            time.sleep(random.choice(range(30,80)))        except http.client.IncompleteRead as e:            print("6:",e)            time.sleep(random.choice(range(5,15)))    return rep.textdef get_data(html_txt):    final=[]    bs=BeautifulSoup(html_txt,"html.parser")   #创建BeautifulSoup对象    body=bs.body   #获取body部分    data=body.find("div",{"id":"7d"}) #找到id为7d的div    ul=data.find("ul")  #获取ul部分    li=ul.find_all("li")   #获取所有的li    for day in li:  #对每个标签中的内容进行遍历        temp=[]        date=day.find("h1").string   #获取日期        temp.append(date)   #将日期添加到temp 中        inf=day.find_all("p")   #找到li中的所有p标签        temp.append(inf[0].string)   #将第一个p标签中的内容添加到temp列表中红        if inf[1].find("span") is None:            temperature_high=None   #傍晚没有最高气温        else:            temperature_high=inf[1].find("span").string  #最高气温            temperature_high=temperature_high.replace("℃","")        temperature_lower=inf[1].find("i").string   #找到最低温        temperature_lower=temperature_lower.replace("℃","")        temp.append(temperature_high)        temp.append(temperature_lower)        final.append(temp)   #将temp添加到final中    return finaldef write_data(data, name):    file_name = name    with open(file_name, 'a', errors='ignore', newline='') as f:            f_csv = csv.writer(f)            f_csv.writerows(data)def get_url():    city={    "海口":"101310101",    "三亚":"101310201",    "苏州":"101190401",    "郑州":"101180101"    }    for k in city:        print(k)    city_name=input("请输入你要查询的城市名字：")    city_num=city[city_name]    weather_url="http://www.weather.com.cn/weather/%s.shtml"%city_num    return weather_urlif __name__=="__main__":    # url="http://www.weather.com.cn/weather/101190401.shtml"    url=get_url()    html=get_html(url)    result=get_data(html)    write_data(result,"weather.csv")    for i in result:        print(i)        #打印天气情况