swiss2fasta.py

import fileinput
import sys

from Bio.ExPASy import get_sprot_raw
from Bio.SeqIO import parse
from Bio.SeqIO.FastaIO import FastaWriter

fasta_out = FastaWriter(sys.stdout,
                        record2title=lambda record: record.id)

for accession_id in fileinput.input():
    sprot_file = get_sprot_raw(accession_id)
    sprot_records = parse(sprot_file, 'swiss')
    for record in sprot_records:
        fasta_out.write_record(record)