def file_search(f_name, data_str):

    """Function:  file_search

    Description:  Search for a string in a file and return the line it was
        found in a line.

    NOTE:  Returns only the first instance found in the file.

    Arguments:
        (input) f_name -> File name searching.
        (input) data_str -> Search string.
        (output) line - > Full line string was found in or None, if not found.

    """

    line = None

    with open(f_name, "r") as s_file:
        for item in s_file:
            if data_str in item:
                line = item
                break

    return line