Python 嵌套字典替换为 none 并追加而不使用 get

Question

if 'value1' in results_dict:
    if results_dict['value1'] is not None:
        if results_dict['value1']['limit'] is None:
            res.append(results_dict['value1']['limit'] == "Nan")
        else:
            res.append(results_dict['value1']['limit'])
    else:
        res.append(results_dict['value1']['limit'] == "Nan")
else:
    res.append("Nan")

我正在尝试解决不允许我将值附加到“res”的问题 (res.append(results_dict['value1']['limit'] == "Nan"))

I am getting TypeError: 'NoneType' object is not subscriptable
I am trying to check if there is a None value and replacing it with NaN. I also want to keep the key 
names. I also used .get twice but that gave me an Attribute Error.

Answer 1

您的代码的常规 Pythonic 习惯用法有点不对劲，您不想使用“is None”( list of things Python returns as None )，而且，对于 nan 测试，您需要导入数学。我相信这就是您正在寻找的:

import math

if 'value1' in results_dict:
    if results_dict['value1']:  #is not None just means it exists, so eliminate that
        if not results_dict['value1']['limit']: #is None just means not
            temp = {'limit':math.nan} #create new dict
            results_dict['value1'].update(temp) #update your level 1 nested dict
            res.append(math.isnan(results_dict['value1']['limit'])) #correct nan test
        else:
            res.append(results_dict['value1']['limit'])
    else:
        res.append(math.isnan(results_dict['value1']['limit'])) #correct test for nan
else:
    res.append(math.nan) #correct assignment of nan

另请参阅: Assigning a variable NAN in Python

编辑:如果您不希望专门分配 NAN，那么您的代码可以大大简化。

if 'value1' in results_dict:
    if results_dict['value1']:
        if results_dict['value1']['limit']:
            res.append(results_dict['value1']['limit'])
    else:
        res.append('')
else:
    res.append('') #correct assignment of nan

实际上，真的不清楚这里的问题是什么......您的资源应该是一个列表？真理值(value)观？字典值？