Fasta parser - python oneliners

fasta.py

import re

# Fasta one-liners
# Parse fasta from a string
def fasta_parse_string(s):
    return dict([(lambda x:(x[0].strip(), re.sub(r'\s+','',x[2])))(l.partition('\n')) for l in s.split('>')[1:]])

# Parse fasta from a file
def fasta_parse_file(f):
    with open(f) as h:return fasta_parse_string(h.read())

# Write data (d) back into fasta format, breaking into lines (length=n)  
def fasta_format(d, n):
    return '\n'.join(['>{}\n'.format(k)+'\n'.join([v[i:i+n] for i in range(0,len(v),n)]) for k,v in d.items()])

# Memory efficient fasta  
class Fasta(object):
    def __init__(self, filename):
        self.file = open(filename, 'r')
        self.buffer = ''
        while not self.buffer.startswith('>'):
            self.consume()
        self.exhausted = False

    def consume(self):
        self.buffer = self.file.readline()
        if self.buffer == '':
            self.file.close()
            raise StopIteration

    def next(self):
        if self.exhausted:
            raise StopIteration

        desc = self.buffer.strip('>').strip()
        self.consume()
        seq = []

        while not self.buffer.startswith('>'):
            seq.append(self.buffer)
            try:
                self.consume()
            except StopIteration:
                self.exhausted = True
                break

        return desc, re.sub(r'\s+', '', ''.join(seq))

    def __iter__(self):
        return self

def parse_fasta(filename):
    return {id: seq for id, seq in Fasta(filename)}