Class _AxesStack

lib/matplotlib/figure.py:70–115

Helper class to track Axes in a figure. Axes are tracked both in the order in which they have been added (``self._axes`` insertion/iteration order) and in the separate "gca" stack (which is the index to which they map in the ``self._axes`` dict).

class _AxesStack:
    """
    Helper class to track Axes in a figure.

    Axes are tracked both in the order in which they have been added
    (``self._axes`` insertion/iteration order) and in the separate "gca" stack
    (which is the index to which they map in the ``self._axes`` dict).
    """

    def __init__(self):
        self._axes = {}  # Mapping of Axes to "gca" order.
        self._counter = itertools.count()

    def as_list(self):
        """List the Axes that have been added to the figure."""
        return [*self._axes]  # This relies on dict preserving order.

    def remove(self, a):
        """Remove the Axes from the stack."""
        self._axes.pop(a)

    def bubble(self, a):
        """Move an Axes, which must already exist in the stack, to the top."""
        if a not in self._axes:
            raise ValueError("Axes has not been added yet")
        self._axes[a] = next(self._counter)

    def add(self, a):
        """Add an Axes to the stack, ignoring it if already present."""
        if a not in self._axes:
            self._axes[a] = next(self._counter)

    def current(self):
        """Return the active Axes, or None if the stack is empty."""
        return max(self._axes, key=self._axes.__getitem__, default=None)

    def __getstate__(self):
        return {
            **vars(self),
            "_counter": max(self._axes.values(), default=0)
        }

    def __setstate__(self, state):
        next_counter = state.pop('_counter')
        vars(self).update(state)
        self._counter = itertools.count(next_counter)


class FigureBase(Artist):