[mdaniel]

Type hints can also be strings, which at least PyCharm resolves as if they were real type references

    from typing import List
    class Alpha:
        @staticmethod
        def doit(b: "Beta") -> List["Beta"]:
            return [b]
    class Beta:
        @staticmethod
        def doit(a: "Alpha") -> List["Alpha"]:
            return [a]

[squeaky-clean]

This only works if they're in the same file, or Alpha imports Beta later in the file and vice versa. Once you split these into separate files (say for example adding a gamma.py file and Gamma class that uses Alpha and Beta) you get Unresolved reference 'Alpha' and Unresolved reference 'Beta', and typechecking calls to Alpha.doit and Beta.doit from Gamma does not work.

[mdaniel]

I thought it also accepted fully qualified type names but I just tried it and you're right. Relevant to this submission's title, if your packages are side-effect free, just importing the namespace then allows referencing the type names without touching the "actual" type

  import gamma
  def doit(bar: "gamma.Gamma"): ...

In Java my answer to circular deps is the introduction of an interface that the concrete types can implement but then breaks the cycle