[英]Python nested dict comprehension with if else
I am trying to convert the below to a dict comprehension我正在尝试将以下内容转换为字典理解
my_dict = {'a': None, 'b': None, 'c': ['1', '2', '3']}
new_dict = {}
for k, v in my_dict.items():
if not v:
new_dict[k] = None
else:
for item in v:
new_dict[f'{k}{item}'] = None
I'm trying to translate my dict to我正在尝试将我的字典翻译成
new_dict = {'a': None, 'b': None, 'c1': None, 'c2': None, 'c3': None}
I'm fairly comfortable with basic list and dict comprehensions but struggling with this one, currently looking something like this but clearly I am a bit off on the syntax:我对基本的列表和字典理解相当满意,但在这个方面很挣扎,目前看起来像这样,但显然我对语法有点偏离:
{k: None if not v else f'{k}{item}': None for item in v for k, v in my_dict.items()}
This abomination will do:这种可憎的行为会:
{fk: None
for k, v in my_dict.items()
for fk in ([k] if v is None else (k + fv for fv in v))}
If the value is None
, you just want the key.如果值为None
,您只需要密钥。
If the value is not None
, you want a list of each value concatenated with the key.如果该值不是None
,您需要一个与键连接的每个值的列表。
Homogenise that to always returning a list, either of one key or multiple:将其同质化为始终返回一个列表,一个键或多个:
[k] if v is None else [k + fv for fv in v]
Then you're looking at a "simple" nested comprehension:然后你正在看一个“简单”的嵌套理解:
{k: None for k in [['a'], ['b'], ['c1', 'c2', 'c3']] for fk in k}
I was proud of my answer:我为我的回答感到自豪:
new_dict = dict(
sum(
[
[(k, None)] if not value else [(f"{k}{v}", None) for v in value]
for k, value in my_dict.items()
],
[],
)
)
... until I saw deceze's answer, which I still need to digest. ...直到我看到 deceze 的回答,我仍然需要消化。
You can do this with the help of itertools.chain.from_iterable
:你可以在itertools.chain.from_iterable
的帮助下做到这一点:
>>> {
y: None
for y in itertools.chain.from_iterable(
k if not v else (f"{k}{x}" for x in v) for k, v in my_dict.items()
)
}
{'a': None, 'b': None, 'c1': None, 'c2': None, 'c3': None}
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