>>> a = np.zeros((10,10), dtype=np.float128)
>>> a.dtype
dtype('float128')
>>> plt.matshow(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/site-packages/matplotlib/pyplot.py", line 2358, in matshow
    im = ax.matshow(A, **kw)
  File "/usr/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 7389, in matshow
    im = self.imshow(Z, **kw)
  File "/usr/lib/python3.6/site-packages/matplotlib/__init__.py", line 1892, in inner
    return func(ax, *args, **kwargs)
  File "/usr/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 5118, in imshow
    im.set_data(X)
  File "/usr/lib/python3.6/site-packages/matplotlib/image.py", line 545, in set_data
    raise TypeError("Image data can not convert to float")
TypeError: Image data can not convert to float
>>> plt.matshow(np.array(a, dtype=np.float64))
<matplotlib.image.AxesImage object at 0x7fad7046b400>