python保存遇到问题: AttributeError: 'str' object has no attribute 'to_csv'

环境：jupyter
码如下：

import pandas as pd

name = pd.read_csv('location', encoding='latin1')
name['Name'] = name['Name'].str.lower()
movie_name = name['Name'].replace(" ", "_")

try:
URL = "https://www.rottentomatoes.com/m/ + movie_name"
except:
pass

df = URL
df.to_csv('url.csv', index=False)（这一步报错AttributeError: 'str' object has no attribute 'to_csv'，求指点）

你这个df是个字符串对象，没有to_csv这个方法