from bs4 import BeautifulSoup, Tag

class Attribute(object):
  def __init__(self, attrname, attrvalue):
    'Initializes a new attribute.'
    self._attrname = attrname
    self._attrvalue = attrvalue

  @property
  def name(self):
    'The attribute name'
    return self._attrname

  @property
  def value(self):
    'The attribute value'
    return self._attrvalue

class TagFactory(object):
  'A factory for `bs4.Tag` objects'
  def __init__(self, soup):
    'Initializes a new factory given a `bs4.BeautifulSoup`.'
    self._soup = soup

  @property
  def soup(self):
    'The `bs4.BeautifulSoup` instance.'
    return self._soup

  def __call__(self, tagname, *contents, **kwargs):
    'Instantiates a `bs4.BeautifulSoup` instance given contents.'
    tag = None
    for c in contents:
      if type(c) is Attribute:
        if tag is not None:
          raise ValueError('Attribute cannot follow content')
        kwargs[c.name] = c.value
      else:
        if tag is None:
          tag = self.soup.new_tag(tagname, **kwargs)
        tag.append(c)
    if tag is None:
      tag = self.soup.new_tag(tagname, **kwargs)
    return tag

soup = BeautifulSoup('')
f = TagFactory(soup)
html = f('html',
    f('head',
      f('meta', Attribute('foo', 'bar'))
      ),
    f('body',
      f('h1', 'Hello World!'),
      f('p', 'This is a test.')
      )
    )
print(html.prettify())