python 如何下载PDF到本地？ 后面代码不会写了

from PIL import Image
import json
import cv2
#import sys, fitz
import pyzbar.pyzbar as pyzbar
from urllib.request import *
from urllib.parse import *
import requests
import sys

if len(sys.argv) != 2:
    print("统一社会信用代码注册号作为参数")
    sys.exit(0) #输入统一社会信用代码
print("正在查询", sys.argv[1])
payload = {"regNo":sys.argv[1]}
payload = urlencode(payload).encode()
data = urlopen("https://XXXXXX", data=payload).read().decode()
pos = data.find('pdf.action')
if pos == -1:
    print("未查询到相关信息")
    sys.exit(0)
uid = data[pos + 14:data.find('&', pos)]
img = urlopen("http://XXXX/ICPSP/temp/certi/{}.pdf".format(uid)).read()
print(img)