python - What's the relationship between 'BeautifulSoup' and 'lxml'? -

in lxml's doc, says:

lxml can interface parsing capabilities of beautifulsoup through lxml.html.soupparser module. provides 3 main functions: fromstring() , parse() parse string or file using beautifulsoup lxml.html document, , convert_tree() convert existing beautifulsoup tree list of top-level elements.

meanwhile, bs' can use lxml parser.[ref]

beautiful soup supports html parser included in python’s standard library, supports number of third-party python parsers. 1 lxml parser.

bs suggests use lxml parser speed.

so if lxml uses bs parsing when bs's parser lxml conversely?

i have been scratching head on understanding relationship. help.

nothing should confusing bs parser , lxml.html parser. bs has html parser, , lxml has own html parser.

bs documentation quoted says can parse html bs soup object using lxml parser or other possible third-party parsers, alternative using default bs parser :

beautifulsoup(markup, "lxml") 

similarly, lxml documentation says can parse html lxml tree object using bs parser, alternative using default lxml.html parser :

root = lxml.html.soupparser.fromstring(tag_soup)