Why does get_legend_handles_labels() return empty lists when legend labels are added via ax.legend() [duplicate] - matplotlib

Question

This one is blowing my mind. I'm creating a little customize legend function where you put in some text and properties and it'll make it for you. So, before this is reachable in the GUI, a figure with a legend has already been created by this point which has "run5" and "run6" in it.
I wrote something that deletes the existing legend and calls legend on that same axis again with new handles/labels. However, when I do ax.get_legend_handles_labels() right afterwards it returns the deleted legend's handle and labels, completely ignoring the legend call I just did.
I've tried removing the legend and then just recreating it. But clearly ax is holding onto the previous legend's data.
from matplotlib.lines import Line2D
ax = self.axes[ind] #just the axis handle
custom_lines, custom_strings = [], []
try:
ax.get_legend().remove()
except:
# Means no legend exists
pass
for idx, i in enumerate(self.lgndRowWidget):
if not i.isHidden():
#The below five lines are grabbing data from GUI
lineText = self.lgndStr[idx].text() # Is "test" here
lineType = self.lgndLine[idx].currentText()
lineWidth = self.lgndWidth[idx].value()
lineMrkr = self.lgndMrkr[idx].currentText()
lineClr = self.lgndClr[idx].text()
custom_lines.append(Line2D([0],[0],
lw=lineWidth,
ls=lineType,
marker=lineMrkr,
color=lineClr))
custom_strings.append(lineText)
if len(custom_lines) != 0:
print(custom_strings)
self.legList = ax.legend(custom_lines, custom_strings)
a,b = ax.get_legend_handles_labels()
print(b)
self.fig.canvas.draw()
print(custom_strings) returns whatever I input. In this case "test".
print(b) returns what was previously in the legend that I can't seem to get rid of: the initial "run5" and "run6". It SHOULD be "test".

Answer 1

You might have misunderstood the functionality of ax.get_legend_handles_labels().
What it does is to look for artists (like lines, collections etc.) that have a label.
It then returns those artists and their respective labels. Hence
ax.legend() is roughly equivalent to
handles, labels = ax.get_legend_handles_labels()
ax.legend(handles=handles, labels=labels)
.get_legend_handles_labels() does not know about whether there is a legend present, because it returns what is supposed to be in the legend, not what currently is in it.