[英]mypy and nested dict comprehension
I'm definitely not an expert of mypy, but there's an error that I'm really not understanding. 我绝对不是mypy的专家,但是我确实不了解一个错误。
Let's say that I have this dictionary and I want to parse it and create another one through a dict comprehension. 假设我有这本字典,我想解析它并通过dict理解创建另一个字典。
my_dict = {
'type1': {
'category1': [
'subcategory1',
'subcategory2',
],
},
'type2': {
'category2': [
'subcategory3',
],
'category3': [],
},
}
The dict comprehension: 字典理解:
new_dict = {
subcategory: {
'category': category,
'type': type,
}
for type, categories in my_dict.items()
for category, subcategories in categories.items()
for subcategory in subcategories
}
and the expected output: 和预期的输出:
{
'subcategory1': {
'category': 'category1',
'type': 'type1'
},
'subcategory2': {
'category': 'category1',
'type': 'type1'
},
'subcategory3': {
'category': 'category2',
'type': 'type2'
}
}
mypy in this situation complains because of the empty category3
, but with an error message ( 'error:"object" has no attribute "items"'
) that refers to the previous line. 在这种情况下,mypy会因为category3
为空而抱怨,但出现了一条错误消息( 'error:"object" has no attribute "items"'
),该消息指向上一行。
Any suggestion? 有什么建议吗?
Thanks in advance 提前致谢
The issue is mypy is unable to infer the type of my_dict
-- it's too complicated for mypy to naturally infer the type. 问题是mypy无法推断my_dict
的类型-对于mypy而言自然无法推断类型太复杂。
You can confirm for yourself by adding the line reveal_type(my_dict)
before running mypy. 您可以通过在运行mypy之前添加reveal_type(my_dict)
行来自己确认。 (Mypy special-cases that function name to help with debugging). (Mypy特有的函数名称有助于调试)。 The inferred type ended up being Dict[str, object]
, or something to that effect. 推断的类型最终是Dict[str, object]
或类似的东西。
You can fix this by explicitly giving my_dict
a type. 您可以通过显式my_dict
类型来解决此问题。 If you're using Python 3.6+, you can use the new variable annotation syntax to do so, like so: 如果您使用的是Python 3.6+,则可以使用新的变量注释语法来这样做,如下所示:
from typing import Dict, List
my_dict: Dict[str, Dict[str, List[str]]] = { ... }
If you're using earlier versions of Python, annotate the variable using the comment-based syntax. 如果您使用的是Python的早期版本,请使用基于注释的语法对变量进行注释。
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