No handles with labels found to put in legend

Question

I'm trying to create a parallelogram in PyPlot. I'm not up to drawing the parallelogram--first I'm putting in the vector arrows--using the following code:

fig = plt.figure()
ax = fig.add_subplot(111)
ax.spines['left'].set_position('zero')
ax.spines['right'].set_color('none')
ax.spines['bottom'].set_position('zero')
ax.spines['top'].set_color('none')
plt.axis([-5,5,-5,5])
ax.xaxis.set_ticks_position('bottom')
ax.yaxis.set_ticks_position('left')
plt.grid()
plt.arrow(0,0, 3,1, head_width=0.2, color='r', length_includes_head=True, label='u')
plt.arrow(0,0, 1,3, head_width=0.2, color='r', length_includes_head=True, label='v')
plt.arrow(0,0, 4,4, head_width=0.2, color='r', length_includes_head=True, label='u+v')
plt.legend()

This returns the following error:

No handles with labels found to put in legend.

I'm not sure why, because, based on the documentation for plt.arrow(), label is an acceptable kwarg, and plt.legend() should ostensibly be reading that. The rest of the figure draws fine; it's just missing the legend.

Answer 1

You can explicitly define the elements in the legend.

For full control of which artists have a legend entry, it is possible to pass an iterable of legend artists followed by an iterable of legend labels respectively. Reference

Example:

arr1 = plt.arrow(0,0, 3,1, head_width=0.2, color='r', length_includes_head=True)
arr2 = plt.arrow(0,0, 1,3, head_width=0.2, color='g', length_includes_head=True)
arr3 = plt.arrow(0,0, 4,4, head_width=0.2, color='b', length_includes_head=True)

plt.xlim(0,5)
plt.ylim(0,5)

plt.legend([arr1, arr2, arr3], ['u','v','u+v'])

Answer 2

The error is thrown because you haven't specified the label text

Either do something like this

plt.hist([x01, x02,x03], color=["lightcoral","lightskyblue","slategrey"], stacked=True, 
             label=['Supressed','Active','Resolved'])
plt.legend()

Or

Do not use plt.legend() if you haven't specified the label text as in the following WRONG example:

plt.hist([x01])
plt.legend()

The above will throw the same error, so either remove legend function or provide what it needs -> label. Side note: Here x01 is just a list of number for which I am creating a histogram, in the first example they are three list of numbers to create stacked bar chart

The bottom line is this error is thrown because of not specifying legend text and calling/initializing a legend

Answer 3

I had this error when using labels which started with an underscore

plt.plot(x, y, label = '_bad_name')

Removing the front underscore from the labels solved the issue

Answer 4

Assuming you have 2 plots ax and ax2, we can:

• get the labels from each y-axis via ax.get_label()
• .legend allows an array to be ingested

fig.legend([ax.get_ylabel(), ax2.get_ylabel()], loc='upper right')

Answer 5

I face similar problem like No handles with labels found to put in legend.

First My code look like

figure, axis = pyplot.subplots(nrows=1,ncols=2, figsize=(15, 6), tight_layout=True)

axis[0].legend(title='Country', title_fontsize = 12) #this line
axis[0].pie(x=piechart_result['value_eur'],labels=piechart_result['short_name'])

axis[1].pie(x=piechart_result['value_eur'],labels=piechart_result['short_name')

pyplot.show()

Then I changed to

figure, axis = pyplot.subplots(nrows=1,ncols=2, figsize=(15, 6), tight_layout=True)

axis[0].pie(x=piechart_result['value_eur'],labels=piechart_result['short_name'])
axis[0].legend(title='Country', title_fontsize = 12) # this line 

axis[1].pie(x=piechart_result['value_eur'],labels=piechart_result['short_name')

pyplot.show()

this work for me in colab notebook