How to find tags with only certain attributes - BeautifulSoup

As explained on the BeautifulSoup documentation

You may use this :

soup = BeautifulSoup(html)
results = soup.findAll("td", {"valign" : "top"})

EDIT :

To return tags that have only the valign="top" attribute, you can check for the length of the tag attrs property :

from BeautifulSoup import BeautifulSoup

html = '<td valign="top">.....</td>\
        <td width="580" valign="top">.......</td>\
        <td>.....</td>'

soup = BeautifulSoup(html)
results = soup.findAll("td", {"valign" : "top"})

for result in results :
    if len(result.attrs) == 1 :
        print result

That returns :

<td valign="top">.....</td>

You can use lambda functions in findAll as explained in documentation. So that in your case to search for td tag with only valign = "top" use following:

td_tag_list = soup.findAll(
                lambda tag:tag.name == "td" and
                len(tag.attrs) == 1 and
                tag["valign"] == "top")