Top 100+ Scrapy Interview Questions And Answers
Question 1. How Does Scrapy Compare To Beautifulsoup Or Lxml?
Answer :
BeautifulSoup and lxml are libraries for parsing HTML and XML. Scrapy is an application framework for writing internet spiders that move slowly web web sites and extract facts from them.
Scrapy gives a integrated mechanism for extracting records (called selectors) but you can easily use BeautifulSoup (or lxml) alternatively, if you experience more at ease operating with them. After all, they’re simply parsing libraries which can be imported and used from any Python code.
In other phrases, comparing BeautifulSoup (or lxml) to Scrapy is like comparing jinja2 to Django.
Question 2. Can I Use Scrapy With Beautifulsoup?
Answer :
Yes, you could. As referred to above, BeautifulSoup may be used for parsing HTML responses in Scrapy callbacks. You simply have to feed the response’s body into a BeautifulSoup item and extract something statistics you want from it.
Here’s an instance spider the use of BeautifulSoup API, with lxml as the HTML parser:
from bs4 import BeautifulSoup
import scrapy
magnificence ExampleSpider(scrapy.Spider):
call = "example"
allowed_domains = ["example.Com"]
start_urls = (
'http://www.Instance.Com/',
)
def parse(self, response):
# use lxml to get respectable HTML parsing speed
soup = BeautifulSoup(response.Textual content, 'lxml')
yield
"url": reaction.Url,
"name": soup.H1.String
Python Interview Questions
Question three. What Python Versions Does Scrapy Support?
Answer :
Scrapy is supported beneath Python 2.7 and Python three.3+. Python 2.6 assist was dropped starting at Scrapy zero.20. Python 3 help become brought in Scrapy 1.1.
Question four. Did Scrapy “steal” X From Django?
Answer :
Probably, however we don’t like that word. We suppose Django is a terrific open source challenge and an instance to comply with, so we’ve used it as an idea for Scrapy.
We consider that, if something is already executed nicely, there’s no want to reinvent it. This concept, except being one of the foundations for open supply and loose software program, no longer only applies to software program but also to documentation, techniques, guidelines, and many others. So, rather than going thru each hassle ourselves, we pick to copy thoughts from the ones tasks which have already solved them well, and attention on the real troubles we need to clear up.
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Question 5. Does Scrapy Work With Http Proxies?
Answer :
Yes. Support for HTTP proxies is furnished (for the reason that Scrapy 0.Eight) thru the HTTP Proxy downloader middleware. See HttpProxyMiddleware.
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Question 6. Does Scrapy Crawl In Breadth-first Or Depth-first Order?
Answer :
By default, Scrapy uses a LIFO queue for storing pending requests, which basically approach that it crawls in DFO order. This order is greater handy in most cases. If you do need to move slowly in proper BFO order, you could do it through setting the following settings:
DEPTH_PRIORITY = 1
SCHEDULER_DISK_QUEUE = 'scrapy.Squeues.PickleFifoDiskQueue'
SCHEDULER_MEMORY_QUEUE = 'scrapy.Squeues.FifoMemoryQueue'
Question 7. Can I Use Basic Http Authentication In My Spiders?
Answer :
Yes.
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Question 8. Why Does Scrapy Download Pages In English Instead Of My Native Language?
Answer :
Try converting the default Accept-Language request header with the aid of overriding the DEFAULT_REQUEST_HEADERSsetting.
Question nine. Can I Run A Spider Without Creating A Project?
Answer :
Yes. You can use the runspider command. For instance, if you have a spider written in a my_spider.Py record you may run it with:
scrapy runspider my_spider.Py
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Question 10. I Get “filtered Offsite Request” Messages. How Can I Fix Them?
Answer :
Those messages (logged with DEBUG stage) don’t necessarily mean there's a problem, so that you may not want to fix them.
Those messages are thrown with the aid of the Offsite Spider Middleware, which is a spider middleware (enabled by default) whose reason is to clear out requests to domain names outside those covered with the aid of the spider.
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Question 11. Can I Use Json For Large Exports?
Answer :
It’ll rely on how huge your output is.
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Question 12. Can I Return (twisted) Deferreds From Signal Handlers?
Answer :
Some signals support returning deferreds from their handlers, others don’t.
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Question 13. What Does The Response Status Code 999 Means?
Answer :
999 is a custom response reputation code utilized by Yahoo websites to throttle requests. Try slowing down the crawling velocity through using a download put off of two (or higher) in your spider:
class MySpider(CrawlSpider):
call = 'myspider'
download_delay = 2
# [ ... Rest of the spider code ... ]
Or with the aid of placing a global download postpone in your project with the DOWNLOAD_DELAY placing.
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Question 14. Can I Call Pdb.Set_trace() From My Spiders To Debug Them?
Answer :
Yes, but you can also use the Scrapy shell which allows you to fast examine (and even adjust) the reaction being processed through your spider, that is, pretty regularly, more beneficial than plain vintage pdb.Set_trace().
Question 15. Simplest Way To Dump All My Scraped Items Into A Json/csv/xml File?
Answer :
To sell off right into a JSON record:
scrapy move slowly myspider -o objects.Json
To unload right into a CSV document:
scrapy crawl myspider -o items.Csv
To sell off into a XML record:
scrapy crawl myspider -o objects.Xml
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Question sixteen. What’s This Huge Cryptic __viewstate Parameter Used In Some Forms?
Answer :
The __VIEWSTATE parameter is utilized in web sites built with ASP.NET/VB.NET.
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Question 17. What’s The Best Way To Parse Big Xml/csv Data Feeds?
Answer :
Parsing massive feeds with XPath selectors may be difficult for the reason that they need to build the DOM of the entire feed in reminiscence, and this can be quite slow and consume a variety of reminiscence.
In order to avoid parsing all the complete feed right now in memory, you could use the functions xmliterand csviter from scrapy.Utils.Iterators module. In reality, that is what the feed spiders use underneath the duvet.
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Question 18. Does Scrapy Manage Cookies Automatically?
Answer :
Yes, Scrapy gets and continues music of cookies despatched by servers, and sends them lower back on subsequent requests, like any regular net browser does.
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Question 19. How Can I See The Cookies Being Sent And Received From Scrapy?
Answer :
Enable the COOKIES_DEBUG placing.
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Question 20. How Can I Instruct A Spider To Stop Itself?
Answer :
Raise the CloseSpider exception from a callback.
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Question 21. Should I Use Spider Arguments Or Settings To Configure My Spider?
Answer :
Both spider arguments and settings may be used to configure your spider. There isn't any strict rule that mandates to use one or the alternative, but settings are extra suitable for parameters that, as soon as set, don’t trade tons, at the same time as spider arguments are intended to exchange more frequently, even on every spider run and every now and then are required for the spider to run in any respect (as an example, to set the start url of a spider).
To illustrate with an instance, assuming you have a spider that wishes to log into a domain to scrape records, and also you simplest need to scrape records from a positive phase of the website online (which varies on every occasion). In that case, the credentials to log in would be settings, at the same time as the url of the section to scrape might be a spider argument.
