How to set a label for an already constructed line in matplotlib?

Question

In my code I already executed

ax.plot(x, y, 'b.-', ...) 

and you need to be able to set the label for the corresponding line after the fact in order to have the same effect as me

 ax.plot(x, y, 'b.-', label='lbl', ...) 

Is there a way to do this in matplotlib?

Answer 1

If you capture the line2D object when you create it, you can set the label using line.set_label() :

 line, = ax.plot(x, y, 'b.-', ...) line.set_label('line 1') 

If you do not, you can find line2D from Axes :

 ax.plot(x, y, 'b.-', ...) ax.lines[-1].set_label('line 1') 

Note. ax.lines[-1] will have access to the last line created, so if you create multiple lines, you need to be careful which line you set for the label using this method.

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Minimal example:

 import matplotlib.pyplot as plt fig,ax = plt.subplots(1) l,=ax.plot(range(5)) l.set_label('line 1') ax.legend() plt.show()