Definition of Scrapy CSS selector
It is a style-application language which was used to develop web pages. In Scrapy, “selectors” are used to link specific styles to specific HTML elements. The other method for scanning HTML text in web pages is XPath. XPath has more capabilities in Scrapy than a simple CSS selector. The lxml package, which interprets XML and HTML in Python, provides the foundation for selectors.
What is scrapy css selector?
- When scraping web pages, we will need to use selectors to extract a specific section of the HTML code, which we may do with XPath or CSS expressions.
- Extract the data is the most common activity when scraping web pages. To do so, we can use one of several libraries.
- Lxml is a pythonic XML parsing package based on ElementTree that also parses HTML.
- Scrapy has a built-in data extraction mechanism. Selectors are named after the fact that they “select” specific elements of the HTML document using XPath or CSS expressions.
How to use scrapy css selector?
- XPath is an XML-based language that may also be used with HTML to select nodes in XML documents. CSS is a style-application language for HTML texts. It establishes selections that link the styles to certain HTML components.
- Scrapy Selectors is a lightweight wrapper for the parsel library, designed to make it easier to work with Scrapy.
- Parsel is will implements the easy API and uses the lxml library beneath the hood. Scrapy selectors are similar to lxml selectors in terms of speed and processing accuracy.
- Below step shows how to construct the scrapy selectors are as follows.
1) In this step we are installing the scrapy by using pip command. In below example we have already installed scrapy package in our system so, it will showing that requirement is already satisfied then we have no need to do anything.
pip install scrapy
2) In this step we are creating the HTML page. We have created below webpage to use scrapy css selector.
Code:
<html>
<head>
<base href = 'http://example.com/' />
<title>Example website</title>
</head>
<body>
<div id = 'images'>
<a href = 'image1.html'>Image 1 <br /><img src = 'image1_thumb.jpg' /></a>
<a href = 'image2.html'>Image 2 <br /><img src = 'image2_thumb.jpg' /></a>
<a href = 'image3.html'>Image 3 <br /><img src = 'image3_thumb.jpg' /></a>
<a href = 'image4.html'>Image 4 <br /><img src = 'image4_thumb.jpg' /></a>
<a href = 'image5.html'>Image 5 <br /><img src = 'image5_thumb.jpg' /></a>
</div>
</body>
</html>
3) After creating the HTML code in this step we are opening the scrapy shell by using html code are as follows. Below example shows open the scrapy shell by using html code.
scrapy shell http://doc.scrapy.org/en/latest/_static/selectors-sample1.html
- We can see that in above example we have used “selectors-sample1.html” file to open the scrapy shell. We can use CSS selectors to pick parts of an HTML file in Scrapy because CSS languages are declared in any HTML file.
- Scrapy is a powerful and scalable web scraping framework. It has a large user base, and each update brings new features.
4) Below example shows how to use a scrapy CSS selector. In below example we have used response method by using CSS selector.
response.css ('img').xpath ('@src').extract()
Scrapy css selector URLs
- CSS selectors can be used in a variety of ways depending on the situation. The very Basic start begins with the basic tags in an HTML file, such as the HTML> tag, the HEAD> tag, the BODY> tag, and so on.
- So, using Scrapy, the basic format for selecting any tag in an HTML file is as follows. So, if we simply want to select the inside text of the Tags or just the attribute of any particular tag, we’ll need to change our selection method.
- URL is nothing but the url which was used at the time of logging into the scrapy shell. Below example shows example of scrapy css selector url.
scrapy shell http://doc.scrapy.org/en/latest/_static/selectors-sample1.html
- If the HTML file has several tags of the same type, we can use the getall function to select all of them instead of the get method. It gives us a list of the tags we have chosen, as well as their data.
- CSS selectors don’t return anything if the tag we’re looking for isn’t referenced in the file. In the event that no data is found, we can also supply default data.
- When scraping a url with Scrapy, the link text and the url’s portion known as href. Below example will returning the text of all the URL from HTML document.
Code:
def parse(self, response):
for quote in response.css('a::text'):
yield {
"py_test" : quote.get()
}
- The below code retrieves urls from the document’s a> HTML elements’ href properties. Returning the styles values can be done in the same way.
Code:
def parse(self, response):
for quote in response.css('a::attr(href)'):
yield {
"py_test" : quote.get()
}
Scrapy CSS selector examples
- In below example we are using response method.
response.css('title::text')
- In below example we are returning the selector list by using scrapy CSS selector are as follows.
response.css ('img').xpath ('@src').extract()
- Below example shows select text attribute.
response.css ('title::text').extract()
- Below example shows get the url and images.
response.css('a[href*=image]::attr(href)').extract()
- Below example shows use getall method.
response.css('a[href*=image]::attr(href)').getall()
Conclusion
The lxml package, which interprets XML and HTML in Python, provides the foundation for selectors. Scrapy css selector is a style-application language that was used to develop web pages. In Scrapy, “selectors” are used to link specific styles to specific HTML elements.
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