from BeautifulSoup import BeautifulSoup
soup = BeautifulSoup(open('file.html', 'r').read())
cols = [header.string for header in soup.find('thead').findAll('th')]
col_idx = cols.index('Username')
col_values = [td[col_idx].string for td in [tr.findAll('td') for tr in soup
    .find('tbody').findAll('tr')]]
BeautifulSoup get all the values of a particular column