Stop matplotlib repeating labels in legend

Question

Here is a very simplified example:

xvalues = [2,3,4,6]

for x in xvalues:
    plt.axvline(x,color=\'b\',label=\'xvalues\')

plt.legend()

Th

Answer 1

I don't know if this can be considered "elegant", but you can have your label a variable that gets set to "_nolegend_" after first usage:

my_label = "xvalues"
xvalues = [2,3,4,6]

for x in xvalues:
    plt.axvline(x, color='b', label=my_label)
    my_label = "_nolegend_"

plt.legend()

This can be generalized using a dictionary of labels if you have to put several labels:

my_labels = {"x1" : "x1values", "x2" : "x2values"}
x1values = [1, 3, 5]
x2values = [2, 4, 6]

for x in x1values:
    plt.axvline(x, color='b', label=my_labels["x1"])
    my_labels["x1"] = "_nolegend_"
for x in x2values:
    plt.axvline(x, color='r', label=my_labels["x2"])
    my_labels["x2"] = "_nolegend_"

plt.legend()

(Answer inspired by https://stackoverflow.com/a/19386045/1878788)