python - 在 Python 中，如何复制字典列表并过滤特定键，包括嵌套键？

Question

如果我有一本包含列表、字典、字符串和整数的字典，我如何复制该字典，但只复制特定的白名单键？

通过这个功能过滤old_dict会给我new_dict. 白名单键可以是任何格式，但解决方案应该能够采用任意白名单键的对象来产生输出。

old_dict = [
    {
        'name': {'first': "John", 'last': "Doe"},
        'groups': ["foo", "bar"],
        'widgets': [
            {'id': 0, 'name': "Acme"},
            {'id': 1, 'name': "Anvil"},
        ],
    },

    {
        'name': {'first': "David"},
        'groups': ["bar", "bash", "ding"],
        'widgets': [
            {'id': 1, 'name': "Anvil"},
            {'id': 8, 'name': "Bingo"},
        ],
    },
]

new_dict = [
    {
        'name': {'last': "Doe"},
        'widgets': [
            {'name': "Acme"},
            {'name': "Anvil"},
        ],
    },

    {
        'name': { },
        'widgets': [
            {'name': "Anvil"},
            {'name': "Bingo"},
        ],
    },
]

Answer 1

制作一个递归函数来处理每种类型并在您看到字典时过滤掉：

def keep_only(keys, val):
    if type(val) is list:
        return [keep_only(keys, v) for v in val]
    if type(val) is dict:
        return dict((k, keep_only(keys, v)) for k,v in val.items() if k in keys)
    return val

示例用法：

>>> old_dict = [
    {
        'name': {'first': "John", 'last': "Doe"},
        'groups': ["foo", "bar"],
        'widgets': [
            {'id': 0, 'name': "Acme"},
            {'id': 1, 'name': "Anvil"},
        ],
    },

    {
        'name': {'first': "David"},
        'groups': ["bar", "bash", "ding"],
        'widgets': [
            {'id': 1, 'name': "Anvil"},
            {'id': 8, 'name': "Bingo"},
        ],
    },
]
>>> keep_only(set(['name', 'widgets', 'last']), old_dict)
[{'widgets': [{'name': 'Acme'}, {'name': 'Anvil'}], 'name': {'last': 'Doe'}}, {'widgets': [{'name': 'Anvil'}, {'name': 'Bingo'}], 'name': {}}]

Answer 2

new_dict = []
for dic in old_dic:
    new_dict.append({})
    for key in white_list: #list of keys
        if key in dic:
            new_dict[key] = old_dic[key]

您可以将列表理解为：

new_dic = [ dict( key, old_dic[key])
                 for key in whitelist
                 if key in old_dic)
            for dic in old_dic ]