Mypy: Cannot Subclass Error

[chantisnake]

I have a dummy base class:

class BaseModel:
    def __init__(self) -> None:
        pass

and I have another class extending this dummy base class:

class DendrogramModel(BaseModel):
    def __init__(self, test_dtm: Optional[pd.DataFrame] = None,
                 test_option: Optional[DendroOption] = None) -> None:
        super().__init__()
        self._test_dtm = test_dtm
        self._test_option = test_option

When I type check, mypy gives me the following error:
error: Class cannot subclass 'BaseModel' (has type 'Any')

I don't know why. Is it because I cannot extend the dummy base class?

[gvanrossum]

The other class is in a different file right? And you have --follow-imports=strict on? You need to tell mypy to check both files.

[chantisnake]

Yes, they are in different files.

I don't think follow import allows strict.

Here is the command I used mypy .\lexos\models\dendro_model.py --ignore-missing-imports --strict

[gvanrossum]

Yeah sorry, I meant skip, not strict. But it sounds like the other module can't be found. Where is it?

[chantisnake]

I also think that is caused by module not found.

Here is part of my project structure:

Lexos
- lexos/
  - __init__.py
  - models/
     - dendrogram_model.py
     - base_model.py
- test/
  - __ init__.py

Here is the import statement used in dendrogram_model.py

from lexos.models.base_model import BaseModel

according to the mypy documentation, mypy climbs up the __init__.py file, then it will definitely successfully found my project root.

[gvanrossum]

There's no __init__.py in models/.

On Mon, Oct 30, 2017 at 8:14 PM, chantisnake [e-mail]
wrote:

I also think that is caused by module not found.

Here is part of my project structure:

Lexos

• lexos/
  
  
  
  • __init__.py
  
  
  • models/
    
    
    
    
    
    • dendrogram_model.py
    
    
    
    • base_model.py
    
    
    
  
  
• test/
  
  
  
  • __ init__.py
  
  

Here is the import statement used in dendrogram_model.py

from lexos.models.base_model import BaseModel

according to the documentation of mypy documentation
http://mypy.readthedocs.io/en/latest/command_line.html#finding-imports,
mypy climbs up the __init__.py file, then it will definitely successfully
found my project root.

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[chantisnake]

uh! how stupid of me...

[gvanrossum]

Not stupid! It takes time to understand how all these things work together.
Explaining your problems to someone else is often a helpful debugging
technique. (So useful, in fact, that people have called it "rubber duck
debugging" -- explain the issue to your rubber ducky and suddenly it
becomes clear to you. There's even Wikipedia page for this. :-)

[wabu]

Not stupid!

:+1: Having it documented here also helped me resolve the same issue in my code :-)