[Python] Why am I getting a Pylance error "Object of type 'A*' is not callable" in VSCode when...

I'm attempting to write a generic class in Python 3.11 that should be able to process a list of elements using different processing classes (A or B in this example). My goal is to use the type variable T to specify the processing class that should be used.

Clarification: Each element x within the list Xrequires an individual initialization of the subclass A or B, so initializing is only possible withing the process() method.

Here's my code:

from typing import List, Self, TypeVar, Generic

class A:
def __init__(self):
pass

def process(self, x):
return x + 1

class B:
def __init__(self):
pass

def process(self, x):
return x + 2

T = TypeVar("T", A, B)

class ListProcessor(Generic[T]):
"""Apply a Transformer to the individual list elements."""

def __init__(self, processor: T):
self.processor_class = processor
self.processors: List[T] = [] # <- Pylance complains! see error message (1)

def process(self, X) -> List:
x_processed = []
for x in X:
proc: T = self.processor_class() # <- Pylance complains! see error message (2)
result = proc.process(x)
x_processed.append(result)
self.processors.append(proc)
return x_processed

lp = ListProcessor(B)
lp.process([1, 2, 3])


The output of the above is:

[3, 4, 5]


which is what I expect. But while the code runs, Pylance type checker complains in VSCode.

1. 
   For the line self.processors: List[T] = [], I get:
   
   
   
   Variable not allowed in type expression PylancereportGeneralTypeIssues
   T: ~T
   (constant) T: Unknown
   ​
2. 
   For the line proc: T = self.processor_class(), I get:
   
   
   
   Object of type "A*" is not callablePylancereportGeneralTypeIssues
   Object of type "B*" is not callablePylancereportGeneralTypeIssues
   ​

I'm struggling to understand these error messages. Could someone help clarify why these errors occur and how I can fix them?

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