Compare parsel vs. Polymer

Parsel is a Python library licensed under BSD that facilitates the extraction and removal of data from HTML and XML documents using XPath and CSS selectors, with the option to integrate regular expressions. To begin, you create a selector object for the HTML or XML content you wish to analyze. After that, you can utilize either CSS or XPath expressions to target specific elements. CSS serves as a styling language for HTML, defining selectors that link styles to designated HTML elements, while XPath is utilized for selecting nodes within XML documents and can also be applied to HTML. Although both CSS and XPath can be used, CSS tends to offer greater readability, whereas XPath provides capabilities that may not be achievable through CSS alone. Built on top of lxml, parsel selectors incorporate some EXSLT extensions and come with pre-registered namespaces available for use in XPath queries. Furthermore, parsel selectors allow for the chaining of selectors, enabling users to primarily select by class using CSS and seamlessly transition to XPath when the situation demands it, enhancing flexibility in data extraction tasks. This dual capability makes parsel a powerful tool for developers working with web data.

The Polymer library offers a robust set of functionalities for developing custom elements, streamlining the process to ensure they behave like standard DOM elements. Just like conventional DOM elements, Polymer elements can be created through a constructor or by utilizing document creation methods, and they can be configured via attributes or properties. Each instance can contain an internal DOM, adapt to changes in properties and attributes, and receive styling both from internal defaults and external sources, all while responding to methods that alter their internal state. When you register a custom element, you link a class to a specific custom element name, and the element includes lifecycle callbacks to effectively manage its various stages. Additionally, Polymer facilitates property declarations, allowing for seamless integration of your element's property API with the Polymer data system. By employing Shadow DOM, your element gains a locally scoped and encapsulated DOM tree, and Polymer can automatically generate and fill a shadow tree for your element derived from a DOM template, enhancing the modularity and reusability of your code. This combination of features not only simplifies the creation of custom elements but also ensures they integrate smoothly into the wider ecosystem of web components.