Finally the bug is solved. you can get and set items on wikidata via PWB
At first you must define a wikidataPage and these are methods you can use. I'll try to expand and make more methods but i don't know any and your help will be very useful: Supports the same interface as Page, with the following added methods:
setitem : Setting item(s) on a page
getentity : Getting item(s) of a page
these examples worked for me:
site=wikipedia.getSite('wikidata',fam='wikidata') page=wikipedia.wikidataPage(site,"Helium") text=page.getentity() page.setitem(summary=u"BOT: TESTING FOO",items={'type':u'item', 'label':'fa', 'value':'OK'}) page.setitem(summary=u"BOT: TESTING GOO",items={'type':u'description', 'language':'en', 'value':'OK'}) page.setitem(summary=u"BOT: TESTING BOO",items={'type':u'sitelink', 'site':'de', 'title':'BAR'})
Cheers!