Python:追加到一个字典值，如果已经存在，该值是一个列表，会添加到所有键的值而不是

Question

Python 输出无法按照示例代码正确地将字符串值添加到循环内字典键的列表值中。

收到的输出:

{'one': ['dev-1', 'dev-3'], 'three': ['dev-1', 'dev-3'], 'five': ['dev-3'],
    'four': ['dev-3'], 'two': ['dev-1', 'dev-3']}

预期输出:

{'one': ['dev-1', 'dev-3'], 'three': ['dev-1'], 'five': ['dev-3'], 
    'four': ['dev-3'], 'two': ['dev-1']}

这是代码:

grp = ['instance "dev-1"\n', 'row id 68\n', 'grp mem "one"  "two" "three"\n', 'next\n',
    'instance "dev-3"\n', 'row id 18d\n', 'grp mem "four" "five" "one"', 'next\n']
grp_no = 0
mapping_dict = {}
current_grp = []
while grp_no < len(grp):
    line = grp[grp_no]
    if grp_no < len(grp):
        instance = line.startswith('instance ')
        grp_member = line.startswith('grp mem ')
        if not (instance or grp_member):
            grp_no += 1
            continue
        if instance:
            obj_id = (line.split()[1]).strip('"')
            current_grp.append(obj_id)
        if grp_member:
            current_members = line.split()
            for i in range(2, len(current_members), 1):
                mem = current_members[i]
                mem = mem.strip('"')
                check_point = mem in mapping_dict and (obj_id in mapping_dict[mem])
                check_point1 = mem in mapping_dict and not obj_id in mapping_dict[mem]
                if check_point:
                    continue
                elif check_point1:
                    (mapping_dict[mem]).append(obj_id)
                else:
                    mapping_dict[mem] = current_grp
            current_grp = []
    grp_no += 1
print(mapping_dict)

Answer 1

您的问题是您在多个字典键之间共享相同的列表:

>>> for k, v in mapping_dict.items():
...     print(id(v), k, v)
...
41955656 four ['dev-3']
41897936 one ['dev-1', 'dev-3']
41897936 three ['dev-1', 'dev-3']
41897936 two ['dev-1', 'dev-3']
41955656 five ['dev-3']

有一种更简单的方法来完成您想要的事情:

mapping_dict = {}
instance = None
for line in grp:
    if line.startswith('instance'):
        instance = line.split('"')[1]
    elif line.startswith('grp mem'):
        for member in line[7:].replace('"', '').split():
            mapping_dict.setdefault(member, []).append(instance)