Figure legend not keeping Line2D marker #9155

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1. jklymak commented on Sep 5, 2017

   

   jklymak

   on Sep 5, 2017

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   Not sure what the issue is with figure legends, but you can achieve the same effect with an axes legend using something like:

   ax.legend(loc='center top', bbox_to_anchor=(0.5, 0.))
   

   (note center top in this case sets the vertical and horizontal justification; the actual location is in bbox_to_anchor.)

   Maybe that is an acceptable workaround.

   I am working on a way to make this automatically resize the parent axis but that'll be 2.2 or later (see #9082).
2. astrojuanlu commented on Sep 5, 2017

   

   astrojuanlu

   on Sep 5, 2017

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   @jklymak thank you for your suggestion - however it is a limited workaround, since axes only support one legend whereas figures support more of them.

   Above all, we are interested in finding out whether this is a bug or a feature :)
3. jklymak commented on Sep 5, 2017

   

   jklymak

   on Sep 5, 2017

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   @Juanlu001 @anhiga

   First, there is no difference between the axes and figure hadnling of the legend artists. ax.get_legend_handles_labels() is called before legend() to gather the needed artists from the axes. You could loop through all your axes as figure.legend does:

               for ax in self.axes:
                   ax_handles, ax_labels = ax.get_legend_handles_labels()
                   for h, l in zip(ax_handles, ax_labels):
                       if not in_handles(h, l):
                           handles.append(h)
                           labels.append(l)

   The solution to your mystery, however, is contained in legend_handler.py, where it was decided that text and lines must correspond one-to-one. So if you want the handle to the marker, you can do:

   for h in leg.get_lines():
       print(h._legmarker.get_marker())
   

   This is pretty hacky, and the undrscore means it could go away.

   Its a little strange to want the marker after the legend has been created. Why don't you just make the legend refer to something you've already drawn and keep track of what you've drawn? The legend doesn't seem like a good place to store the state of your plotting.
4. anhiga commented on Sep 6, 2017

   

   anhiga

   on Sep 6, 2017

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   Thank you for your answers.
   @jklymak I understand now the way get_legend_handles_labels() works.

   Why don't you just make the legend refer to something you've already drawn and keep track of what you've drawn? The legend doesn't seem like a good place to store the state of your plotting.

   You are right, we shouldn't rely on the legend to store our plotting state.

   I'm closing this.
5. anhiga

   closed this as completedon Sep 6, 2017
6. QuLogic

   added

   topic: legend

   on Jun 30, 2021