The .text field of each diagram contains its central label as a Text object. The .texts is a list of the Text objects for each of the entering/leaving arrows. You can check the string to know which text it is about, and change properties such as bold or the xy-position.
As a Sankey diagram is quite complex, fine-tuning the positions can happen once the diagram is created. A simple approach can be to add additional newlines in the strings.
import matplotlib.pyplot as plt
from matplotlib.sankey import Sankey
fig, ax = plt.subplots(figsize=(8, 12))
ax.set_xticks([])
ax.set_yticks([])
ax.set_title("My funnel")
ax.set_axis_off()
number = [round(12345 * 0.6 ** i) for i in range(6)]
labels = ["\n\n\n\n\n\n\nTotal joined", "\n\n\n\nFirst", "\n\nSecond", "\nThird", "\nFourth", "\n\nReached final"]
sankey = Sankey(ax=ax, scale=0.0015, offset=0.3)
for input_number, output_number, label in zip(number[:-1], number[1:], labels):
this_index = len(sankey.diagrams)
prior = this_index - 1 if this_index > 0 else None
pathlengths = [0, 0, 2 if this_index != 4 else 10]
exitlabel = labels[-1] if this_index == 4 else None
sankey.add(flows=[input_number, -output_number, output_number - input_number],
orientations=[0, 0, 1],
patchlabel=label,
labels=['', exitlabel, 'quit'],
prior=prior,
connect=(1, 0),
pathlengths=pathlengths,
trunklength=10.,
rotation=-90,
facecolor=plt.cm.spring((this_index + 1) / 5))
diagrams = sankey.finish()
for diagram in diagrams:
diagram.text.set_fontweight('bold')
diagram.text.set_fontsize('10')
for text in diagram.texts:
text.set_fontsize('10')
str = text.get_text() # can be normal label, "quit", a number or empty
if len(str) > 0:
if str[0].isdigit():
text.set_visible(False)
elif str.startswith('quit'):
xy = text.get_position()
text.set_position((xy[0] + 2, xy[1]))
else:
text.set_fontweight('bold')
plt.ylim(ymin=plt.ylim()[0] * 1.05)
plt.show()
