url = 'http://www.ebi.ac.uk/ena/data/view/PRJEB2357&display=xml'
project_page = urlopen(url)
soup = BeautifulSoup(project_page, "html.parser")
print soup

<db>PUBMED</db>
<id>25101644</id>
</xref_link>
</project_link>
<project_link>
<xref_link>
<db>PUBMED</db>
<id>24509479</id>

url = 'http://www.ebi.ac.uk/ena/data/view/PRJEB2357&display=xml'
project_page = urlopen(url)
soup = BeautifulSoup(project_page, "html.parser")
text = soup.text
print text

PUBMED
25101644




PUBMED
24509479

url = 'http://www.ebi.ac.uk/ena/data/view/PRJEB2357&display=xml'
project_page = urlopen(url)
soup2 = BeautifulSoup(project_page, "html.parser")
text = soup2.text
text = text.replace('n', ' ').replace(' ', '') #removes all spaces and linebreaks
PMID = re.findall('PUBMED........', text, flags = 0)
print PMID

[u'PUBMED25101644', u'PUBMED24509479']

[pubmed.find_next_sibling("ID").get_text()
 for pubmed in soup.find_all("DB", text="PUBMED")]

soup = BeautifulSoup(project_page, "xml")