NoneType in python | 易学教程

问题

I was trying to get some rating data from Tripadvisor but as i was trying to fetch the data i was getting

'NoneType' object is not subscriptable

Can anybody help me figuring out where am i going wrong , sorry i am very new to python.

Here is my sample code

import requests
import re
from bs4 import BeautifulSoup
r = requests.get('http://www.tripadvisor.in/Hotels-g186338-London_England-Hotels.html')
data = r.text        
soup = BeautifulSoup(data)
for rate in soup.find_all('div',{"class":"rating"}):
               print (rate.img['alt'])

The output to this looks like:

4.5 of 5 stars
4.5 of 5 stars 4 of 5 stars
4.5 of 5 stars
4.5 of 5 stars 4 of 5 stars
4.5 of 5 stars
4.5 of 5 stars
4.5 of 5 stars Traceback (most recent call last):

  File "<ipython-input-52-7460e8bfcb82>", line 3, in <module>
    print (rate.img['alt'])

TypeError: 'NoneType' object is not subscriptable

回答1:

Not all your <div class="rating"> tags have an <img /> tag, so rate.img is None.

Those divs look like this instead:

<div class="rating">
  <span class="rate">4.5 out of 5, </span>
  <em>2,294 Reviews</em>
  <br/>
  <div class="posted">Last reviewed 25 Sep 2015</div>
</div>

You can either test for this:

if rate.img is not None:
    # ...

or select only images under the div.rating tags with a CSS selector:

for img in soup.select('div.rating img[alt]'):

The selector here picks out <img/> tags with an alt attribute, nested inside a <div class="rating"> tag.

回答2:

It means that not all divs with a class of rating have images with an alt attribute. You should handle this appropriately - to ignore such cases, just wrap your print (rate.img['alt']) in a try, except block, or check to see if rate.img is None first.

First option:

try:
    print(rate.img['alt'])
except TypeError:
    print('Rating error')

Second option:

for rate in soup.find_all('div',{"class":"rating"}):
    if rate.img is not None:
        print (rate.img['alt'])

The first option follows EAFP (Easier to ask for forgiveness than permission), a common Python coding style, whereas the second follows LBYL (Look before you leap). In this case, I would suggest the second.

来源：https://stackoverflow.com/questions/32799480/nonetype-in-python

标签

python

beautifulsoup