matplotlib/matplotlib · error · RuntimeError

Entry point name '{name}' duplicated

Error message

Entry point name '{name}' duplicated

What it means

Error "Entry point name '{name}' duplicated" thrown in matplotlib/matplotlib.

Source

Thrown at lib/matplotlib/backends/registry.py:180

        return entries

    def _validate_and_store_entry_points(self, entries):
        # Validate and store entry points so that they can be used via matplotlib.use()
        # in the normal manner. Entry point names cannot be of module:// format, cannot
        # shadow a built-in backend name, and there cannot be multiple entry points
        # with the same name but different modules. Multiple entry points with the same
        # name and value are permitted (it can sometimes happen outside of our control,
        # see https://github.com/matplotlib/matplotlib/issues/28367).
        for name, module in set(entries):
            name = name.lower()
            if name.startswith("module://"):
                raise RuntimeError(
                    f"Entry point name '{name}' cannot start with 'module://'")
            if name in self._BUILTIN_BACKEND_TO_GUI_FRAMEWORK:
                raise RuntimeError(f"Entry point name '{name}' is a built-in backend")
            if name in self._backend_to_gui_framework:
                raise RuntimeError(f"Entry point name '{name}' duplicated")

            self._name_to_module[name] = "module://" + module
            # Do not yet know backend GUI framework, determine it only when necessary.
            self._backend_to_gui_framework[name] = "unknown"

    def backend_for_gui_framework(self, framework):
        """
        Return the name of the backend corresponding to the specified GUI framework.

        Parameters
        ----------
        framework : str
            GUI framework such as "qt".

        Returns
        -------
        str or None
            Backend name or None if GUI framework not recognised.

View on GitHub (pinned to b379c1b69e)

When it happens

Trigger: Thrown at lib/matplotlib/backends/registry.py:180 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of matplotlib/matplotlib@b379c1b69e (2026-08-21). Data as JSON: /api/errors/cba50dfd6002946a. Report an issue: GitHub.