The method you are looking for is set_label_text

set_label is the inherited method from Artist which provides the text that would appear in a legend entry (odd to do for Axis, but is defined by Artist)

However, confusingly, get_label is actually overridden with a different meaning in Axis, where it returns the Text instance of the label. (And so I might expect the setter to error with a raw string, but expect a Text instance)

I will state that the "_text" postfix is itself confusing, because it is given a string and is opposed to the version which uses Text.

Thanks - I thought something like that might be going on. Shall we close as won't fix then? Or we could keep open and as an action deprecate the overriden get_text() in favour of get_label_text() (if that would even be technically possible...)?

Please leave open. I will think about whether we can make this less confusing when I have a quiet minute.

The name label is very broad and used for different things in different contexts. It would have been better to either be more specific set/get_legend_label or distinguish data and decoration Artist categories, which could have individual interpretations of label. But we are not in a place to change either. To limit misuse and confusion I propose to:

• Override set_label() in Axis and raise RuntimeError("A legend label cannot be assigned to an Axis"). While this explicitly breaks Liskov's Substitution Principle, that principle was already implicitly broken by the design, i.e. deriving Axis as a class that cannot have legend entries from the Artist class that assumes it can have legend labels. IMHO it's better to make this explicit and fail loudly instead of silently accepting a value and not ever doing anything with it.
• Deprecate the overridden get_label(). We should not be overwriting this with different semantics than the base class. Instead, suggest to access the attribute Axis.label directly. Whether that's a good pattern is a differerent topic. It's already there as an interface, so it won't go away too easily. Alternatively, one could add get_axislabel() (consistent with the existing Axis.get_ticklabels().
  When the deprecation expires, either fall back to the original behavior or, preferrably also raise a RuntimeError.