import re


def valid_md5_str(md5_str):
    """ 校验md5 字符

    :param md5_str:
    :return: bool
    """
    str_list = md5_str.split('.')
    n_len = len(str_list)
    if n_len != 2:
        return False
    n_len_md5 = len(str_list[0])
    if n_len_md5 != 32:
        return False
    find_str = re.findall('[^a-z0-9]+', str_list[0])
    if find_str:
        return False
    return True