类型为 \"Literal[False, xxx]\" 的参数不能分配给函数 \"__setitem__\" 中类型为 \"Iterable\" 的参数 \"__o\"

Question

我的代码可以简化为：

from typing import Union, Any, Dict, List, Tuple

def myFunc() -> Union[object, Dict, List, str,
                      int, float, bool, None]:
  something = { 'prop': 123}
  return something

obj = myFunc()
obj['k'] = isinstance(obj, Dict) and 321

我从 Pylance 得到了这样的例外：

(variable) obj: object | List | str | int | float | bool | Dict | None
"__setitem__" method not defined on type "object"PylancereportGeneralTypeIssues
"__setitem__" method not defined on type "str"PylancereportGeneralTypeIssues
"__setitem__" method not defined on type "int"PylancereportGeneralTypeIssues
"__setitem__" method not defined on type "float"PylancereportGeneralTypeIssues
"__setitem__" method not defined on type "bool"PylancereportGeneralTypeIssues
Argument of type "Literal['k']" cannot be assigned to parameter "__s" of type "slice" in function "__setitem__"
  "Literal['k']" is incompatible with "slice"PylancereportGeneralTypeIssues

可能是什么问题？

Answer 1

问题在于假设 obj['k'] 始终有效，但 List | str | int | float | bool | None 并非如此。解决办法是将最后一行改写如下：

obj = isinstance(obj, Dict) and {**obj, 'k': 123}

完整的例子如下：

from typing import Union, Any, Dict, List, Tuple

def myFunc() -> Union[object, Dict, List, str,
                      int, float, bool, None]:
  something = { 'prop': 123}
  return something

obj = myFunc()
obj = isinstance(obj, Dict) and {**obj, 'k': 123}