Adding values to dictionary in FOR loop. Updating instead of “Appending”

问题

import requests
from bs4 import BeautifulSoup

urls = ['url1']
dictionary = {}

for url in urls:
    req = requests.get(url)
    soup = BeautifulSoup(req.text, "lxml")

    for sub_heading in soup.find_all('h3'):  
        dictionary[url] = sub_heading.text

print(dictionary)

I'm getting a result that looks like this {url : sub_heading.text} instead of getting a dictionary containing all the values I'm expecting. It seems that the loop is updating instead of "appending"...

回答1:

Python Dictionaries have key:value pairs, and it can not have duplicate keys.

So in this code, 'url' is key and 'sub_heading.text' is value.

And everytime this loop runs, only the value for 'url' in dict is getting updated.

 for sub_heading in soup.find_all('h3'):  
        dictionary[url] = sub_heading.text

You should use some other data structure instead of Dict (for e.g. list of tuples or dataframe).

来源：https://stackoverflow.com/questions/61374655/adding-values-to-dictionary-in-for-loop-updating-instead-of-appending