import urllib
url = 'ftp://ftp.ncbi.nlm.nih.gov/genomes/Bacteria/Citrobacter_rodentium_ICC168_uid43089/NC_013716.ffn'
urllib.request.urlretrieve(url, 'tmp.ffn')
('tmp.ffn', <email.message.Message at 0x4085a20>)
with open('tmp.ffn') as f:
ffn = f.read()
print(ffn[:100])
>gi|283783779|ref|NC_013716.1|:166-231 Citrobacter rodentium ICC168 chromosome, complete genome ATGA