You can do it like this:
def sum(dict_list):
result_list = []
name_dict = {}
for dict_item in dict_list:
name = dict_item['Name']
amt = dict_item['amt']
if name_dict.has_key(name):
pos = name_dict[name]
result_list[pos] = {'Name':name, 'amt': (result_list[pos]['amt']+amt)}
else:
result_list.append(dict_item)
name_dict[name] = len(result_list) - 1
return result_list