Use Mypy with Ruamel.yaml

Question

I am attempting to use MyPy with modules that use ruamel.yaml and Mypy cannot find ruamel.yaml even though Python has no problem finding it. I am puzzled because I can't find a module called YAML.py or class called YAML either, even though these statements work in Python:

from ruamel.yaml import YAML
yaml = YAML()
x = yaml.load()

What do I need to do to get MyPy to recognize ruamel.yaml?

Answer 1

A workaround is to run without the incremental logic of mypy:

python -m mypy --no-incremental myfile.py

Background

There is a known issue in mypy, see here.

In summary:

Something is not working with the incremental logic of mypy when it is encountering ruamel.

• When you run it once, all goes ok. This is the command: python -m mypy myfile.py

• Then, when you run it again, you get an error:

  error: Skipping analyzing 'ruamel': found module but no type hints or library stubs [import]

• Then, when you run it again, it all goes ok

• etc.