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ENH: Gracefully handle python-build-standalone ImportError with Tk #30394

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Merged
ksunden merged 6 commits into from
Aug 28, 2025
Merged

ENH: Gracefully handle python-build-standalone ImportError with Tk #30394

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64d0b0c
ENH: Gracefully handle python-build-standalone ImportError with Tk.
timhoffm Aug 5, 2025
bc2ed87
DOC: add canonical uv update command in error message
tacaswell Aug 21, 2025
59b29f5
DOC: tweak suggestion for upgrading uv managed Python
tacaswell Aug 22, 2025
c332377
Fix line length
timhoffm Aug 24, 2025
ed12aa9
Mentioned fix in recent python-build-standalone
timhoffm Aug 24, 2025
6d1f6d3
whitespace fix
timhoffm Aug 24, 2025
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30 changes: 28 additions & 2 deletions lib/matplotlib/backends/_backend_tk.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,8 +22,34 @@
TimerBase, ToolContainerBase, cursors, _Mode, MouseButton,
CloseEvent, KeyEvent, LocationEvent, MouseEvent, ResizeEvent)
from matplotlib._pylab_helpers import Gcf
from . import _tkagg
from ._tkagg import TK_PHOTO_COMPOSITE_OVERLAY, TK_PHOTO_COMPOSITE_SET

try:
from . import _tkagg
from ._tkagg import TK_PHOTO_COMPOSITE_OVERLAY, TK_PHOTO_COMPOSITE_SET
except ImportError as e:
# catch incompatibility of python-build-standalone with Tk
cause1 = getattr(e, '__cause__', None)
cause2 = getattr(cause1, '__cause__', None)
if (isinstance(cause1, ImportError) and
isinstance(cause2, AttributeError) and
"'_tkinter' has no attribute '__file__'" in str(cause2)):

is_uv_python = "/uv/python" in (os.path.realpath(sys.executable))
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@QuLogic QuLogic Aug 5, 2025

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According to astral-sh/python-build-standalone#382, you might be able to use what uv uses: https://github.com/astral-sh/uv/blob/c25c800367a5f43069f1c9d778cfd5de1bcc54a6/crates/uv-python/python/get_interpreter_info.py#L639-L645 (i.e., sysconfig values).

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@timhoffm timhoffm Aug 5, 2025

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Is that more helpful?

I think we should catch the error, not exclude python-build-standalone per-se. If they'd fix the tk issue, our versions would directly work. On is_uv_python - I've explicitly tested for uv and tailored the error message, because I anticipate that'll by far the most route to trigger this, and I project that most uv users will not know what python-build-standalone is. So let's give them a uv-targeted error message.

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@QuLogic QuLogic Aug 5, 2025

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I didn't suggest excluding python-build-standalone, just detecting it differently.

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@timhoffm timhoffm Aug 5, 2025

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My point is I do not really care about python-build-standalone. The criterion is 1. does it raise the known error? And if so, is it a uv-install that I can point users to as the practical cause.

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@QuLogic QuLogic Aug 6, 2025

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If that's the case that you only care about uv, then the PR/commit title should be adjusted.

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@timhoffm timhoffm Aug 6, 2025

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Possibly my wording was not exactly precise.

The issue originates from the current way python-build-standalone is implmented. - So the PR title is justified.

Then there are two aspects to handling:

  1. Detection: I want to detect the specific error and respond to that. - It's not helpful to detect python-build-standalone. They may improve to fix the error in the future. So issuing a warning/error purely on the fact that python-build-standalone is used would be presumptuous.

  2. Error message: In the simplest case, we could just have the second error message

    Failed to import tkagg backend. This is likely caused by using a Python executable based on python-build-standalone, which is not compatible with Tk. Please use another Python interpreter or select another backend.

    (or if you want to be more affirmative explicitly test for python-build-standalone and remove the "likely"). However, the by-far most common way to obtain a python-build-standalone python is via uv. But it's a technical detail of uv and users are most likely not aware of it. So telling them, they have python-build-standalone is not helpful for fixing the issue. Therefore, I added the uv detection to tell them that uv-provided python is not compatible.

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@tacaswell tacaswell Aug 6, 2025

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I am 👍 on doing the work to detect if it is uv.

if is_uv_python:
raise ImportError(
"Failed to import tkagg backend. You are using a uv-installed python "
"executable, which is not compatible with Tk. "
"Please use another Python interpreter or select another backend."
) from e
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else:
raise ImportError(
"Failed to import tkagg backend. This is likely caused by using a "
"Python executable based on python-build-standalone, which is not "
"compatible with Tk. "
"Please use another Python interpreter or select another backend."
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@geofft geofft Aug 21, 2025

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This should be updated too to mention that a newer python-build-standalone version will fix this - for users of other tools (Poetry, mise, Bazel rules_python, etc.) there should be a path forward without changing the tools and workflow they're using, though it's not practical or necessary to specifically document what exactly they should do to upgrade.

(Also, if you're editing this, small nit above - I would specifically say that you're using an outdated Python version, now that current uv-installed Python versions are compatible with Tk.)

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) from e
else:
raise


_log = logging.getLogger(__name__)
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