Matplotlib : making a colored markers legend from scratch

Question

In Matplotlib, i\'m trying to make a legend with colored \"markers\" like this one :

this one has been made using the scatter function, but is

Answer 1

Following the example given in the legend guide, you can use a Line2D object instead of a marker object.

The only difference to the example given in the guide is you want to set linestyle='None'

import matplotlib.lines as mlines
import matplotlib.pyplot as plt

blue_star = mlines.Line2D([], [], color='blue', marker='*', linestyle='None',
                          markersize=10, label='Blue stars')
red_square = mlines.Line2D([], [], color='red', marker='s', linestyle='None',
                          markersize=10, label='Red squares')
purple_triangle = mlines.Line2D([], [], color='purple', marker='^', linestyle='None',
                          markersize=10, label='Purple triangles')

plt.legend(handles=[blue_star, red_square, purple_triangle])

plt.show()

Answer 2

You could subclass the HandlerBase to create a handler from a tuple of (color, marker).

import matplotlib.pyplot as plt
from matplotlib.legend_handler import HandlerBase

list_color  = ["c", "gold", "crimson"]
list_mak    = ["d","s","o"]
list_lab    = ['Marker 1','Marker 2','Marker 3']

ax = plt.gca()

class MarkerHandler(HandlerBase):
    def create_artists(self, legend, tup,xdescent, ydescent,
                        width, height, fontsize,trans):
        return [plt.Line2D([width/2], [height/2.],ls="",
                       marker=tup[1],color=tup[0], transform=trans)]


ax.legend(list(zip(list_color,list_mak)), list_lab, 
          handler_map={tuple:MarkerHandler()}) 

plt.show()