x=something, y=somethinelse and z=crud all likely to fail - how do i wrap them up

[Veek. M]

Chris Angelico wrote:

> On Sun, Jan 31, 2016 at 3:58 PM, Veek. M <vek.m1234 at gmail.com> wrote:
>> I'm parsing html and i'm doing:
>>
>> x = root.find_class(...
>> y = root.find_class(..
>> z = root.find_class(..
>>
>> all 3 are likely to fail so typically i'd have to stick it in a try. This
>> is a huge pain for obvious reasons.
>>
>> try:
>>  ....
>> except something:
>>  x = 'default_1'
>> (repeat 3 times)
>>
>> Is there some other nice way to wrap this stuff up?
> 
> I'm not sure what you're using to parse HTML here (there are several
> libraries for doing that), but the first thing I'd look for is an
> option to have it return a default if it doesn't find something - even
> if that default has to be (say) None.
> 
> But failing that, you can always write your own wrapper:
> 
> def find_class(root, ...):
>     try:
>         return root.find_class(...)
>     except something:
>         return 'default_1'
> 
> Or have the default as a parameter, if it's different for the different
> ones.
> 
> ChrisA

I'm using lxml.html

    def parse_page(self, root):
        for li_item in root.xpath('//li[re:test(@id, "^item[a-z0-9]+$")]', 
namespaces={'re': "http://exslt.org/regular-expressions"}):
            description = li_item.find_class('vip')[0].text_content()
            link = li_item.find_class('vip')[0].get('href')
            price_dollar = li_item.find_class('lvprice prc')
[0].xpath('span')[0].text
            bids = li_item.find_class('lvformat')[0].xpath('span')[0].text

            tme_time = li_item.find_class('tme')[0].xpath('span')
[0].get('timems')
            if tme_time:
                time_hrs = int(tme_time)/1000 - time.time()
            else:
                time_hrs = 'No time found'

            shipping = li_item.find_class('lvshipping')
[0].xpath('span/span/span')[0].text_content()"
            
            print('{} {} {} {} {}'.format(link, price_dollar, time_hrs, 
shipping, bids))
            print('-----------------------------------------------------------------')