请问beautifulsoup里面怎么拼接网址呀？

就是因为这个爬取的网站他有一个主url，然后里面的子页面源代码都是后面不一样，想着怎么让他们拼接起来，我自己的代码如下，求指点

import requests
from bs4 import BeautifulSoup
import time
url = "https://www.umei.cc/p/gaoqing/"
resp = requests.get(url)
resp.encoding = "utf-8"
# print(resp.text)
# 把源代码交给BS4
main_page = BeautifulSoup(resp.text, "html.parser")
alist = main_page.find("div", class_="TypeList").find_all("a")

# print(alist)
for a in alist:
    href = a.get('href')  # 直接通过get拿到属性的值
    #拿到子页面的源代码
    child_page_resp = requests.get(href)
    child_page_resp.encoding = 'utf-8'
    child_page_text = child_page_resp.text
    # 从子页面中拿到图片的下载链接
    child_page = BeautifulSoup(child_page_text, "html.parser")
    p = child_page.find("div", id_="ArticleId")
    img = p.find("img")
    print(img.get("src"))
    #下载图片
    img_resp = requests.get(src)
    # img_resp.content  # 这里拿到的是字节，字节写到文件里不就是图片嘛
    img_name = src.split("/")[-1]  #拿到url中最后一个/以后的内容
    with open("img/"+img_name, mode="wb") as f:
        f.write(img_resp.content) #图片内容写入文件
    print("over!", img_name)
    time.sleep(1)
print("all over")

import requests
from bs4 import BeautifulSoup
import time
url = "https://www.umei.cc/p/gaoqing/"
resp = requests.get(url)
resp.encoding = "utf-8"
# print(resp.text)
# 把源代码交给BS4
main_page = BeautifulSoup(resp.text, "html.parser")
alist = main_page.find("div", class_="TypeList").find_all("a")
# print(alist)
for a in alist:
    href = ‘{0}/{1}'.format(url, a.get('href'))
    #拿到子页面的源代码
    child_page_resp = requests.get(href)
    child_page_resp.encoding = 'utf-8'
    child_page_text = child_page_resp.text
    # 从子页面中拿到图片的下载链接
    child_page = BeautifulSoup(child_page_text, "html.parser")
    p = child_page.find("div", id_="ArticleId")
    img = p.find("img")
    src = '{0}/{1}'.format(url, img.get("src"))
    #下载图片
    img_resp = requests.get(src)
    # img_resp.content  # 这里拿到的是字节，字节写到文件里不就是图片嘛
    img_name = src.split("/")[-1]  #拿到url中最后一个/以后的内容
    with open("img/"+img_name, mode="wb") as f:
        f.write(img_resp.content) #图片内容写入文件
    print("over!", img_name)
    time.sleep(1)
print("all over")

href='{0}/{1}'%(url,href)
img='{0}/{1}'%(url,img)