def get_exp_data(diff_fname):
    """
    Parse genes with differential expression score.
    The file expects genes with a score in a tab delimited format.
    """
    gene_exp_rate=dict()
    dfh=open(diff_fname, "rU")
    for line in dfh:
        parts=line.strip('\n\r').split('\t')
        try:
            float(parts[1])
        except:continue
        gene_exp_rate[parts[0]]=float(parts[1])
    dfh.close()
    return gene_exp_rate