def _read_fasta_files(f, args):
    """ read fasta files of each sample and generate a seq_obj
    with the information of each unique sequence in each sample

    :param f: file containing the path for each fasta file and
    the name of the sample. Two column format with `tab` as field
    separator

    :returns: * :code:`seq_l`: is a list of seq_obj objects, containing
               the information of each sequence
             * :code:`sample_l`: is a list with the name of the samples
               (column two of the config file)
    """
    seq_l = {}
    sample_l = []
    idx = 1
    for line1 in f:
        line1 = line1.strip()
        cols = line1.split("\t")
        with open(cols[0], 'r') as fasta:
            sample_l.append(cols[1])
            for line in fasta:
                if line.startswith(">"):
                    idx += 1
                    counts = int(re.search("x([0-9]+)", line.strip()).group(1))
                else:
                    seq = line.strip()
                    seq = seq[0:int(args.maxl)] if len(seq) > int(args.maxl) else seq
                    if counts > int(args.minc) and len(seq) > int(args.minl):
                        if seq not in seq_l:
                            seq_l[seq] = sequence_unique(idx, seq)
                        seq_l[seq].add_exp(cols[1], counts)
    return seq_l, sample_l