read_fasta_from_str.py

def read_fasta_from_str(fasta):
    """

    :param str fasta: multiple sequences in fasta string
    """
    from itertools import groupby

    def is_header(line):
        return line.startswith(">")

    for header, group in groupby(fasta.splitlines(), is_header):
        if header:
            line = group.next()
            id_ = line[1:].split()[1]
        else:
            sequence = ''.join(line.strip() for line in group)
            yield id_, sequence