from decimal import Decimal
ip = get_ipython()
formatter = ip.display_formatter.formatters['text/latex']

def format_list(obj):
    if not isinstance(obj, list):
        return None
if not all(isinstance(item, Decimal) for item in obj):
    return None
return '$$[%s]$$' % ';'.join(map(str, obj))
formatter.for_type_by_name('builtins', 'list', format_list)
Custom Display Output for List of ObjA