获取QQ群成员头像

写一个程序，输入qq群号码，把每个群成员的头像下载下来，保存到本地，图片名字取群昵称，如果没有群昵称，取qq名字

import requests,os

url = 'https://qun.qq.com/cgi-bin/qun_mgr/search_group_members'
data = {"gc":"613536708","st":"0","end":"20","sort":"0","bkn":"1558838945"}
headers = {"cookie":"ga=amp-NlwkQaFaNC9AB5p9d9b1PQ; pgv_pvid=3865120886; pgv_pvi=46711808; RK=ZRj015KJFK; ptcz=6bf07833c06fd4a7df3abb89f2f83f69020c4cd011baeb54d1bbc595ab3570d2; ts_uid=5535538620; ts_refer=xui.ptlogin2.qq.com/cgi-bin/xlogin; traceid=4a54b00adc; _qpsvr_localtk=0.5378462754149511; pgv_si=s9377113088; uin=o0026830866; skey=@Ap4rgIcYY; ptisp=ctc; p_uin=o0026830866; pt4_token=nenrT-sROcvLlxeEdZt0Hxsv72Mego10XTBkiSWX0y0_; p_skey=hDgE2WRv9Ca2GLtQ3AWxuUHyZt9Lu6Hdm5O-sJP6dkA_; pgv_info=ssid=s1216683484; ts_last=qun.qq.com/member.html"}
result = requests.post(url,data=data,verify=False,headers=headers).json()
mems = result.get('mems')  #qq群成员的所有信息
if not os.path.isdir(r'C:\Users\ght\PycharmProjects\untitled\homework(day6)\613536708群头像'):  #判断存群头像文件夹是否存在，不存在则创建
    os.mkdir('613536708群头像')
for mem in mems:
    qq_num = mem.get('uin')  #取QQ号
    img_url = 'https://q4.qlogo.cn/g?b=qq&nk=%s&s=140'%qq_num  #取每个QQ号对应的头像
    img_content = requests.get(img_url).content  # 下载头像,二进制内容
    if mem.get('card'):   #若群名片存在，取群名片，否则取qq名
        file_name=mem.get('card') +'.jpg'
    else:
        file_name=mem.get('nick') +'.jpg'
    abs_path = os.path.join(r'C:\Users\ght\PycharmProjects\untitled\homework(day6)\613536708群头像',file_name)
    with open(abs_path,'wb') as f:
        f.write(img_content)