The Python block 1 generates the figure 1

import matplotlib, numpy
matplotlib.use('Agg')
import matplotlib.pyplot as plt
fig=plt.figure(figsize=(4,2))
x=numpy.linspace(-15,15)
plt.plot(numpy.sin(x)/x)
fig.tight_layout()
plt.savefig('Fig2.png')
return 'Fig2.png'

Problem: whereas the HTML export labels the source listing as "Listing 1" and is correctly refers to 1, the PDF export labels it "Figure 2" (and points to it) when the default verbatim method is used. When one bothers to use minted, the result is correct.