Question about how reset_ticks() works

lxguan1 · April 16, 2022, 6:21pm

Hi All,

I’ve been working on fixing an issue (#22104) and I’ve run into a problem with understanding how the reset_ticks() function in the axis.py file works.

Specifically, I’m not sure how the function is making the new tick after it deletes self.majorTicks. It seems like the new tick is being created during the deletion operation, but I don’t see where any function is being called to make one. It appears to just magically appear when I step though the line with a debugger. Any help would be greatly appreciated.

QuLogic · April 20, 2022, 6:59am

It’s a _LazyTickList descriptor that generates itself on access:

github.com

matplotlib/matplotlib/blob/main/lib/matplotlib/axis.py#L575-L604

      
        
            class _LazyTickList:
                """
                A descriptor for lazy instantiation of tick lists.
            
            
    See comment above definition of the ``majorTicks`` and ``minorTicks``
                attributes.
                """
            
            
    def __init__(self, major):
                    self._major = major
            
            
    def __get__(self, instance, cls):
                    if instance is None:
                        return self
                    else:
                        # instance._get_tick() can itself try to access the majorTicks
                        # attribute (e.g. in certain projection classes which override
                        # e.g. get_xaxis_text1_transform).  In order to avoid infinite
                        # recursion, first set the majorTicks on the instance to an empty
                        # list, then create the tick and append it.

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