I’ve been working on some interesting python stuff at Mozilla and one task recently called for called for rending a page and then finding elements with a URL attribute value (like img[src] or a[href]) and ensuring they become absolute URLs. ?One problem I encountered when using html5lib was that LINK and IMG elements were being skipped when I tokenized the HTML. ?After browsing through the html5lib source code, I found a variable called voidElements which included both LINK and IMAGE:
voidElements = frozenset(( "base", "command", "event-source", "link", "meta", "hr", "br", "img", "embed", "param", "area", "col", "input", "source"))
When I commented out those two elements, they were found upon next run of my routine, meaning their presence in the set were causing me problems. ?Here’s how I skirted the issue:
new_void_set = set()for item in html5lib_constants.voidElements:new_void_set.add(item)new_void_set.remove('link')new_void_set.remove('img')html5lib_constants.voidElements = frozenset(new_void_set)
Since voidElements is a frozenset, I couldn’t simply remove LINK and IMG, so I needed to create a new frozenset without those elements. ?Let me know if there’s a more python-ish way of creating this frozen set. ?In an event, delving into the deep recesses of html5lib paid off and I accomplished the goal!
Read the full article at: Python html5lib SkippedElements
