Simple parser for fastq file format

parseFastq.py

from itertools import ifilter, islice

def readFastq(fastqfile):
    "parse a fastq-formatted file, yielding a (header, sequence, quality) tuple"
    fastqiter = (l.strip('\n') for l in fastqfile)  # strip trailing newlines 
    fastqiter = ifilter(lambda l: l, fastqiter)  # skip blank lines
    while True:
        fqlines = list(islice(fastqiter, 4))
        if len(fqlines) == 4:
            header1,seq,header2,qual = fqlines
            if header1.startswith('@') and header2.startswith('+'):
                yield header1[1:], seq, qual
            else:
                raise ValueError("Invalid header lines: %s and %s" % (header1, header2))
        elif len(fqlines) == 0:
            raise StopIteration
        else:
            raise EOFError("Failed to parse four lines from fastq file!")