如何用列表作为键路径访问嵌套字典并进行增删操作？

给定嵌套字典和包含键路径的动态列表，我们可以通过以下方式实现对应值的获取，以及对最终层级键值对的增删操作：

1. 获取指定路径的值 #

方法一：循环遍历路径 #

最直观的方式就是逐层遍历列表中的键，深入嵌套字典：

foo = {"/" : {"bar": {"morefoo": "returnme"}} }
example = ["/","bar","morefoo"]

current = foo
for key in example:
    current = current[key]
print(current)  # 输出: returnme

方法二：用functools.reduce简化代码 #

如果偏好简洁写法，可以用reduce函数一次性完成逐层访问：

from functools import reduce

foo = {"/" : {"bar": {"morefoo": "returnme"}} }
example = ["/","bar","morefoo"]

result = reduce(lambda d, k: d[k], example, foo)
print(result)  # 输出: returnme

2. 对最终层级的键值对进行增删操作 #

要修改、添加或删除最终层级的内容，需要先定位到倒数第二层的字典，再操作最后一个键：

添加/修改键值对 #

foo = {"/" : {"bar": {"morefoo": "returnme"}} }
example = ["/","bar","newkey"]

# 拆分路径：前n-1个键是父路径，最后一个是目标键
parent_keys = example[:-1]
target_key = example[-1]

# 定位到父字典
parent_dict = foo
for key in parent_keys:
    parent_dict = parent_dict[key]

# 添加或修改值
parent_dict[target_key] = "new_value"
print(foo)
# 输出: {"/": {"bar": {"morefoo": "returnme", "newkey": "new_value"}}}

删除键值对 #

foo = {"/" : {"bar": {"morefoo": "returnme"}} }
example = ["/","bar","morefoo"]

parent_keys = example[:-1]
target_key = example[-1]

parent_dict = foo
for key in parent_keys:
    parent_dict = parent_dict[key]

# 删除指定键
del parent_dict[target_key]
print(foo)
# 输出: {"/": {"bar": {}}}

3. 封装成工具函数（可选） #

如果需要多次使用这些逻辑，可以封装成函数，提升复用性：

from functools import reduce

def get_nested_value(d, keys):
    return reduce(lambda d, k: d[k], keys, d)

def set_nested_value(d, keys, value):
    parent_dict = reduce(lambda d, k: d[k], keys[:-1], d)
    parent_dict[keys[-1]] = value

def delete_nested_key(d, keys):
    parent_dict = reduce(lambda d, k: d[k], keys[:-1], d)
    del parent_dict[keys[-1]]

# 使用示例
foo = {"/" : {"bar": {"morefoo": "returnme"}} }
example = ["/","bar","morefoo"]

print(get_nested_value(foo, example))  # returnme
set_nested_value(foo, ["/","bar","newkey"], "hello")
print(foo)  # {"/": {"bar": {"morefoo": "returnme", "newkey": "hello"}}}
delete_nested_key(foo, example)
print(foo)  # {"/": {"bar": {"newkey": "hello"}}}

内容的提问来源于stack exchange，提问作者Pressing the buttons