Fix 'partially initialized module (circular import)' error?

[TomJGooding]

My Textual application has each widget split into separate files. I'm trying to add bindings to each widget to focus another specific widget using self.app.query_one, but I'm getting this error:

$ textual run app.py 
cannot import name 'ExampleForm' from partially initialized module 'example_form' (most likely due to a circular import) 

I guessing this has something to do with the way widgets are mounted, but I'm not sure how best to fix the error or whether I'm just doing something completely wrong!

Any advice would be much appreciated - here's a minimal reproduction of my code:

# app.py

from textual.app import App, ComposeResult
from textual.widgets import Footer

from example_form import ExampleForm
from example_list import ExampleList


class ExampleApp(App):
    def compose(self) -> ComposeResult:
        yield ExampleForm()
        yield ExampleList()
        yield Footer()

# example_form.py

from textual.widgets import Input

from example_list import ExampleList


class ExampleForm(Input):
    BINDINGS = [("escape", "cancel", "Cancel")]

    def __init__(self) -> None:
        super().__init__(placeholder="Add Item")

    def action_cancel(self) -> None:
        self.value = ""
        self.app.query_one(ExampleList).focus()

# example_list.py

from textual.widgets import ListView

from example_form import ExampleForm


class ExampleList(ListView):
    BINDINGS = [("i", "focus_form", "Add Item")]

    def action_focus_form(self) -> None:
        self.app.query_one(ExampleForm).focus()

[davep]

I guessing this has something to do with the way widgets are mounted

This is just a Python error really, nothing to do with Textual. If you take the above down to its minimum:

app.py

from widget_one import WidgetOne
from widget_two import WidgetTwo

widget_one.py

from widget_two import WidgetTwo

class WidgetOne:
    pass

widget_two.py

from widget_one import WidgetOne

class WidgetTwo:
    pass

You end up with the same error:

Traceback (most recent call last):
  File "/Users/davep/develop/python/textual-sandbox/x/app.py", line 1, in <module>
    from widget_one import WidgetOne
  File "/Users/davep/develop/python/textual-sandbox/x/widget_one.py", line 1, in <module>
    from widget_two import WidgetTwo
  File "/Users/davep/develop/python/textual-sandbox/x/widget_two.py", line 1, in <module>
    from widget_one import WidgetOne
ImportError: cannot import name 'WidgetOne' from partially initialized module 'widget_one' (most likely due to a circular import) (/Users/davep/develop/python/textual-sandbox/x/widget_one.py)

As the error suggests, you have a circular import.

[willmcgugan]

Two solutions come to mind. You could use a local import.

    def action_cancel(self) -> None:
        from example_list import ExampleList
        self.value = ""`
        self.app.query_one(ExampleList).focus()

Or you could specify the query as a string, which means you wouldn't strictly need to import anything.

    def action_cancel(self) -> None:
        self.value = ""`
        self.app.query_one("ExampleList").focus()

[TomJGooding]

Thank you both for taking the time to answer - clearly the problem was the latter "I'm just doing something completely wrong!" then! Forgive my ignorance, I'm still learning Python and never had this error before.