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AdvancedHTMLParser 7.2.3.2

A Powerful HTML Parser/Scraper/Validator/Formatter that constructs a modifiable, searchable DOM tree, and includes many standard JS DOM functions (getElementsBy*, appendChild, etc) and additional methods

Package Documentation

AdvancedHTMLParser is an Advanced HTML Parser, with support for adding, removing, modifying, and formatting HTML.

It aims to provide the same interface as you would find in a compliant browser through javascript ( i.e. all the getElement methods, appendChild, etc), as well as many more complex and sophisticated features not available through a browser. And most importantly, it’s in python!

There are many potential applications, not limited to:

  • Webpage Scraping / Data Extraction
  • Testing and Validation
  • HTML Modification/Insertion
  • Outputting your website
  • Debugging
  • HTML Document generation
  • Web Crawling
  • Formatting HTML documents or web pages

It is especially good for servlets/webpages. It is quick to take an expertly crafted page in raw HTML / css, and have your servlet’s ingest with AdvancedHTMLParser and create/insert data elements into the existing view using a simple and well-known interface ( javascript-like + HTML DOM ).

Another useful scenario is creating automated testing suites which can operate much more quickly and reliably (and at a deeper function-level), unlike in-browser testing suites.

Short Doc

AdvancedHTMLParser

Think of this like “document” in a browser.

The AdvancedHTMLParser can read in a file (or string) of HTML, and will create a modifiable DOM tree from it. It can also be constructed manually from AdvancedHTMLParser.AdvancedTag objects.

To populate an AdvancedHTMLParser from existing HTML:

parser = AdvancedHTMLParser.AdvancedHTMLParser()

# Parse an HTML string into the document

parser.parseStr(htmlStr)

# Parse an HTML file into the document

parser.parseFile(filename)

The parser then exposes many “standard” functions as you’d find on the web for accessing the data, and some others:

getElementsByTagName - Returns a list of all elements matching a tag name

getElementsByName - Returns a list of all elements with a given name attribute

getElementById - Returns a single AdvancedTag (or None) if found an element matching the provided ID

getElementsByClassName - Returns a list of all elements containing a class name

getElementsByAttr - Returns a list of all elements matching a paticular attribute/value pair.

getElementsWithAttrValues - Returns a list of all elements with a specific attribute name containing one of a list of values

getElementsCustomFilter - Provide a function/lambda that takes a tag argument, and returns True to “match” it. Returns all matched objects

getHTML - Returns string of HTML representing this DOM

getRootNodes - Get a list of nodes at root level (0)

getAllNodes - Get all the nodes contained within this document

getFormattedHTML - Returns a formatted string (using AdvancedHTMLFormatter; see below) of the HTML. Takes as argument an indent (defaults to two spaces)

The results of all of these getElement* functions are TagCollection objects. These objects can be modified, and will be reflected in the parent DOM.

The parser also contains some expected properties, like

head - The “head” tag associated with this document, or None

body - The “body” tag associated with this document, or None

forms - All “forms” on this document as a TagCollection

General Attributes

In general, attributes can be accessed with dot-syntax, i.e.

tagEm.id = “Hello”

will set the “id” attribute. If it works in HTML javascript on a tag element, it should work on an AdvancedTag element with python.

setAttribute, getAttribute, and removeAttribute are more explicit and recommended ways of getting/setting/deleting attributes on elements.

The same names are used in python as in the javascript/DOM, such as ‘className’ corrosponding to a space-separated string of the ‘class’ attribute, ‘classList’ corrosponding to a list of classes, etc.

Style Attribute

Style attributes can be manipulated just like in javascript, so element.style.position = ‘relative’ for setting, or element.style.position for access. There are also helper methods, getStyle(name) and setStyle(name, value) which will set the correct values.

The naming conventions are the same as in javascript, like “element.style.paddingTop” for “padding-top” attribute.

TagCollection

A TagCollection can be used like a list.

It also exposes the various getElement* functions which operate on the elements within the list (and their children).

To operate just on items in the list, you can use filterCollection which takes a lambda/function and returns True to retain that tag in the return.

AdvancedTag

The AdvancedTag represents a single tag and its inner text. It exposes many of the functions and properties you would expect to be present if using javascript.

each AdvancedTag also supports the same getElementsBy* functions as the parser.

It adds several additional that are not found in javascript, such as peers and arbitrary attribute searching.

some of these include:

appendText - Append text to this element

appendChild - Append a child to this element

removeChild - Removes a child

removeText - Removes first occurance of some text from any text nodes

removeTextAll - Removes ALL occurances of some text from any text nodes

insertBefore - Inserts a child before an existing child

insertAfter - Inserts a child after an existing child

getChildren - Returns the children as a list

getStartTag - Start Tag, with attributes

getEndTag - End Tag

getPeersByName - Gets “peers” (elements with same parent, at same level in tree) with a given name

getPeersByAttr - Gets peers by an arbitrary attribute/value combination

getPeersWithAttrValues - Gets peers by an arbitrary attribute/values combination.

getPeersByClassName - Gets peers that contain a given class name

getElement\* - Same as above, but act on the children of this element.

nextSibling - Get next sibling, be it text or an element

nextSiblingElement - Get next sibling, that is an element

previousSibling - Get previous sibling, be it text or an element

previousSiblingElement - Get previous sibling, that is an element

{get,set,has,remove}Attribute - get/set/test/remove an attribute

{add,remove}Class - Add/remove a class from the list of classes

setStyle - Set a specific style property [like: setStyle(“font-weight”, “bold”) ]

isTagEqual - Compare if two tags have the same attributes. Using the == operator will compare if they are the same exact tag (by uuid)

getUid - Get a unique ID for this tag (internal)

getAllChildNodes - Gets all nodes beneath this node in the document (its children, its children’s children, etc)

getAllNodes - Same as getAllChildNodes, but also includes this node

contains - Check if a provided node appears anywhere beneath this node (as child, child-of-child, etc)

remove - Remove this node from its parent element, and disassociates this and all sub-nodes from the associated document

__str__ - str(tag) will show start tag with attributes, inner text, and end tag

__repr__ - Shows a reconstructable representation of this tag

__getitem__ - Can be indexed like tag[2] to access second child.

And some properties:

children/childNodes - The children (tags) as a list NOTE: This returns only AdvancedTag objects, not text.

childBlocks - All direct child blocks. This includes both AdvnacedTag objects and text nodes (str)

innerHTML - The innerHTML including the html of all children

outerHTML - innerHTML wrapped in this tag

classNames/classList - a list of the classes

parentNode/parentElement - The parent tag

tagName - The tag name

ownerDocument - The document associated with this node, if any

And many others. See the pydocs for a full list, and associated docstrings.

Appending raw HTML

You can append raw HTML to a tag by calling:

tagEm.appendInnerHTML(‘<div id=”Some sample HTML”> <span> Yes </span> </div>’)

which acts like, in javascript:

tagEm.innerHTML += ‘<div id=”Some sample HTML”> <span> Yes </span> </div>

Creating Tags from HTML

Tags can be created from HTML strings outside of AdvancedHTMLParser.parseStr (which parses an entire document) by:

  • Parser.AdvancedHTMLParser.createElement - Like document.createElement, creates a tag with a given tag name. Not associated with any document.
  • Parser.AdvancedHTMLParser.createElementFromHTML - Creates a single tag from HTML.
  • Parser.AdvancedHTMLParser.createElementsFromHTML - Creates and returns a list of one or more tags from HTML.
  • Parser.AdvancedHTMLParser.createBlocksFromHTML - Creates and returns a list of blocks. These can be AdvancedTag objects (A tag), or a str object (if raw text outside of tags). This is recommended for parsing arbitrary HTML outside of parsing the entire document. The createElement{,s}FromHTML functions will discard any text outside of the tags passed in.

Advanced Filtering

AdvancedHTMLParser contains two kinds of “Advanced Filtering”:

find

The most basic unified-search, AdvancedHTMLParser has a “find” method on it. This will search all nodes with a single, simple query.

This is not as robust as the “filter” method (which can also be used on any tag or TagCollection), but does not require any dependency packages.

find - Perform a search of elements using attributes as keys and potential values as values

(i.e. parser.find(name=’blah’, tagname=’span’) will return all elements in this document

with the name “blah” of the tag type “span” )

Arguments are key = value, or key can equal a tuple/list of values to match ANY of those values.

Append a key with __contains to test if some strs (or several possible strs) are within an element

Append a key with __icontains to perform the same __contains op, but ignoring case

Special keys:

tagname - The tag name of the element

text - The text within an element

NOTE: Empty string means both “not set” and “no value” in this implementation.

Example:

cheddarElements = parser.find(name=’items’, text__icontains=’cheddar’)

filter

If you have QueryableList installed (a default dependency since 7.0.0 to AdvancedHTMLParser, but can be skipped with ‘–no-deps’ passed to setup.py)

then you can take advantage of the advanced “filter” methods, on either the parser (entire document), any tag (that tag and nodes beneath), or tag collection (any of those tags, or any tags beneath them).

A full explanation of the various filter modes that QueryableList supports can be found at https://github.com/kata198/QueryableList

Special keys are: “tagname” for the tag name, and “text” for the inner text of a node.

An attribute that is unset has a value of None, which is different than a set attribute with an empty value ”.

The AdvancedHTMLParser has:

filter / filterAnd - Perform a filter query on all nodes in this document, returning a TagCollection of elements matching ALL criteria

filterOr - Perform a filter query on all nodes in this document, returning a TagCollection of elements matching ANY criteria

Every AdvancedTag has:

filter / filterAnd - Perform a filter query on this nodes and all sub-nodes, returning a TagCollection of elements matching ALL criteria

filterOr - Perform a filter query on this nodes and all sub-nodes, returning a TagCollection of elements matching ANY criteria

Every TagCollection has:

filter / filterAnd - Perform a filter query on JUST the nodes contained within this list (no children), returning a TagCollection of elements matching ALL criteria

filterOr - Perform a filter query on JUST the nodes contained within this list (no children), returning a TagCollection of elements matching ANY criteria

filterAll / filterAllAnd - Perform a filter query on the nodes contained within this list, and all of their sub-nodes, returning a TagCollection of elements matching ALL criteria

filterAllOr - Perform a filter query on the nodes contained within this list, and all of their sub-nodes, returning a TagCollection of elements matching ANY criteria

Validation

Validation can be performed by using ValidatingAdvancedHTMLParser. It will raise an exception if an assumption would have to be made to continue parsing (i.e. something important).

InvalidCloseException - Tried to close a tag that shouldn’t have been closed

MissedCloseException - Missed a non-optional close of a tag that would lead to causing an assumption during parsing.

IndexedAdvancedHTMLParser

IndexedAdvancedHTMLParser provides the ability to use indexing for faster search. If you are just parsing and not modifying, this is your best bet. If you are modifying the DOM tree, make sure you call IndexedAdvancedHTMLParser.reindex() before relying on them.

Each of the get* functions above takes an additional “useIndex” function, which can also be set to False to skip index. See constructor for more information, and “Performance and Indexing” section below.

AdvancedHTMLFormatter and formatHTML

The AdvancedHTMLFormatter formats HTML into a pretty layout. It can handle elements like pre, core, script, style, etc to keep their contents preserved, but does not understand CSS rules.

The methods are:

parseStr - Parse a string of contents

parseFile - Parse a filename or file object

getHTML - Get the formatted html

A script, formatHTML comes with this package and will perform formatting on an input file, and output to a file or stdout:

Usage: formatHTML (Optional: [/path/to/in.html]) (optional: [/path/to/output.html])

Formats HTML on input and writes to output file, or stdout if output file is omitted.

If output filename is not specified or is empty string, output will be to stdout.

If input filename is not specified or is empty string, input will be from stdin

Notes

  • Each tag has a generated unique ID which is assigned at create time. The search functions use these to prevent duplicates in search results. There is a global function in the module, AdvancedHTMLParser.uniqueTags, which will filter a list of tags and remove any duplicates. TagCollections will only allow one instance of a tag (no duplicates)
  • In general, for tag names and attribute names, you should use lowercase values. During parsing, the parser will lowercase attribute names (like NAME=”Abc” becomes name=”Abc”). During searching, however, for performance reasons, it is assumed you are passing in already-lowercased strings. If you can’t trust the input to be lowercase, then it is your responsibility to call .lower() before calling .getElementsBy*
  • If you are using this to construct HTML and not search, I recommend either setting the index params to False in the constructor, or calling AdvancedHTMLParser.disableIndexing()
  • There are additional functions and usages not documented here, check the file for more information.

Performance and Indexing

Performance is very good using this class. The performance can be further enhanced via several indexing tunables:

Firstly, in the constructor of IndexedAdvancedHTMLParser and in the reindex method is a boolean to be set which determines if each field is indexed (e.x. indexIDs will make getElementByID use an index).

If an index is used, parsing time slightly goes up, but searches become O(1) (from root node, slightly less efficent from other nodes) instead of O(n) [n=num elements].

By default, IDs, Names, Tag Names, Class Names are indexed.

You can add an index for any arbitrary field (used in getElementByAttr) via IndexedAdvancedHTMLParser.addIndexOnAttribute(‘src’), for example, to index the ‘src’ attribute. This index can be removed via removeIndexOnAttribute.

Dependencies

AdvancedHTMLParser can be installed without dependencies (pass ‘–no-deps’ to setup.py), and everything will function EXCEPT filter* methods.

By default, https://github.com/kata198/QueryableList will be installed, which will enable support for those additional filter methods.

Unicode

AdvancedHTMLParser generally has very good support for unicode, and defaults to “utf-8” (can be altered by the “encoding” argument to the AdvancedHTMLParser.AdvancedHTMLParser when parsing.)

If you are still getting UnicodeDecodeError or UnicodeEncodeError, there are a few things you can try:

  • If the error happens when printing/writing to stdout ( default behaviour for apache / mod_python is to open stdout with the ANSI/ASCII encoding ), ensure your streams are, in fact, set to utf-8.

    • Set the environment variable PYTHONIOENCODING to “utf-8” before python is launched. In Apache, you can add the line “SetEnv PYTHONIOENCODING utf-8” to your httpd.conf in order to achieve this.
  • Ensure that the data you are passing to AdvancedHTMLParser has the correct encoding (matching the “encoding” parameter).

  • Switch to python3 if at all possible – python2 does have ‘unicode’ support and AdvancedHTMLParser uses it to the best of its ability, but python2 does still have some inherit flaws which may come up using standard library / output functions. You should ensure that these are set to use utf-8 (as described above).

AdvancedHTMLParser is tested against unicode ( even has a unit test ) which works in both python2 and python3 in the general case.

If you are having an issue (even on python2) and you’ve checked the above “common configuration/usage” errors and think there is still an issue, please open a bug report on https://github.com/kata198/AdvancedHTMLParser with a test case, python version, and traceback.

The library itself is considered unicode-safe, and almost always it’s an issue outside of this library, or has a simple workaround.

Example Usage

See https://raw.githubusercontent.com/kata198/AdvancedHTMLParser/master/example.py for an example of parsing store data using this class.

Contact Me / Support

I am available by email to provide support, answer questions, or otherwise provide assistance in using this software. Use my email kata198 at gmail.com with “AdvancedArgumentParser” in the subject line.

Unit Tests

See “tests” directory available in github. Use “runTests.py” within that directory. Tests use my GoodTests framework. It will download it to the current directory if not found in path, so you don’t need to worry that it’s a dependency.

 
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