从对象列表创建动态级嵌套dict？

Question

我试图将对象列表转换为嵌套的dict,可以通过索引访问.

以下代码适用于两级嵌套字典.我想将它扩展到灵活地工作任意数量的级别.

from collections import namedtuple
import pprint 

Holding = namedtuple('holding', ['portfolio', 'ticker', 'shares'])
lst = [
        Holding('Large Cap', 'TSLA', 100),
        Holding('Large Cap', 'MSFT', 200),
        Holding('Small Cap', 'UTSI', 500)
]

def indexer(lst, indexes):
    """Creates a dynamic nested dictionary based on indexes."""
    result = {}
    for item in lst:
        index0 = getattr(item, indexes[0])
        index1 = getattr(item, indexes[1])
        result.setdefault(index0, {}).setdefault(index1, [])
        result[index0][index1].append(item)
    return result 


d = indexer(lst, ['portfolio', 'ticker'])
pp = pprint.PrettyPrinter()
pp.pprint(d)

输出:

{'Large Cap': {'MSFT': [holding(portfolio='Large Cap', ticker='MSFT', shares=200)],
               'TSLA': [holding(portfolio='Large Cap', ticker='TSLA', shares=100)]},
 'Small Cap': {'UTSI': [holding(portfolio='Small Cap', ticker='UTSI', shares=500)]}}

Answer 1

您可以按照以下方式尝试。只需迭代索引指定的属性列表并继续跟踪由此创建的嵌套dict：

def indexer(lst, indexes):
    result = {}
    for item in lst:
        attrs = [getattr(item, i) for i in indexes]
        crnt = result  # always the dict at the current nesting level
        for attr in attrs[:-1]:
            # follow one level deeper
            crnt = crnt.setdefault(attr, {})  
        crnt.setdefault(attrs[-1], []).append(item)
    return result 

这会产生以下输出：

>>> d = indexer(lst, ['portfolio', 'ticker'])
{'Large Cap': {'ticker': [holding(portfolio='Large Cap', ticker='TSLA', shares=100),
                          holding(portfolio='Large Cap', ticker='MSFT', shares=200)]},
 'Small Cap': {'ticker': [holding(portfolio='Small Cap', ticker='UTSI', shares=500)]}}

>>> d = indexer(lst, ['portfolio', 'ticker', 'shares'])
{'Large Cap': {'MSFT': {200: [holding(portfolio='Large Cap', ticker='MSFT', shares=200)]},
               'TSLA': {100: [holding(portfolio='Large Cap', ticker='TSLA', shares=100)]}},
 'Small Cap': {'UTSI': {500: [holding(portfolio='Small Cap', ticker='UTSI', shares=500)]}}}