import re


def is_url(token):
    """
    Return True for url strings. 
    Args:
        token: single token
    Returns:
        Booelan
    Raises:
        None
    Examples:
        >>> is_url("www.google.com")
        True
        >>> is_url("google.com")
        True
        >>> is_url("spacy.org")
        True
        >>> is_url("2.3.1987")
        False
    """
    regex_url = r'((www\d{0,3}[.]|https?://|redir\.aspx\?|[%a-z0-9.\-]+[.][a-z]{2,4}/)([^\s()<>\[\]]+))'
    if any(sw in token for sw in ["www.", "http", ".com", ".org", ".de"]):
      return True
    if re.match(regex_url, token):
      return True
    return False