Differences to regular HTML parsing

There are a few differences in the returned tree to the regular HTML parsing functions from lxml.html. html5lib normalizes some elements and element structures to a common format. For example, even if a table does not have a tbody html5lib will inject one automatically:

>>> from lxml.html import tostring, html5parser
>>> tostring(html5parser.fromstring("<table><td>foo"))
'<table><tbody><tr><td>foo</td></tr></tbody></table>'

Also the parameters the functions accept are different.

Function Reference

parse(filename_url_or_file):

Parses the named file or url, or if the object has a .read() method, parses from that.

document_fromstring(html, guess_charset=True):

Parses a document from the given string. This always creates a correct HTML document, which means the parent node is <html>, and there is a body and possibly a head.

If a bytestring is passed and guess_charset is true the chardet library (if installed) will guess the charset if ambiguities exist.

fragment_fromstring(string, create_parent=False, guess_charset=False):

Returns an HTML fragment from a string. The fragment must contain just a single element, unless create_parent is given; e.g., fragment_fromstring(string, create_parent='div') will wrap the element in a <div>. If create_parent is true the default parent tag (div) is used.

If a bytestring is passed and guess_charset is true the chardet library (if installed) will guess the charset if ambiguities exist.

fragments_fromstring(string, no_leading_text=False, parser=None):

Returns a list of the elements found in the fragment. The first item in the list may be a string. If no_leading_text is true, then it will be an error if there is leading text, and it will always be a list of only elements.

If a bytestring is passed and guess_charset is true the chardet library (if installed) will guess the charset if ambiguities exist.

fromstring(string):

Returns document_fromstring or fragment_fromstring, based on whether the string looks like a full document, or just a fragment.

Additionally all parsing functions accept a parser keyword argument that can be set to a custom parser instance. To create custom parsers you can subclass the HTMLParser and XHTMLParser from the same module. Note that these are the parser classes provided by html5lib.