In [1]: plt.hist(np.arange(10), range=(0, np.inf))
# empty plot
Out[1]: 
(array([ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.]),
 array([ nan,  inf,  inf,  inf,  inf,  inf,  inf,  inf,  inf,  inf,  inf]),
 <a list of 10 Patch objects>)

In [2]: plt.hist(np.arange(10), range=(0, np.inf), histtype="step")
---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
<ipython-input-2-1921805d8f19> in <module>()
----> 1 plt.hist(np.arange(10), range=(0, np.inf), histtype="step")

/usr/lib/python3.5/site-packages/matplotlib/pyplot.py in hist(x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, hold, **kwargs)
   2894                       histtype=histtype, align=align, orientation=orientation,
   2895                       rwidth=rwidth, log=log, color=color, label=label,
-> 2896                       stacked=stacked, **kwargs)
   2897         draw_if_interactive()
   2898     finally:

/usr/lib/python3.5/site-packages/matplotlib/axes/_axes.py in hist(self, x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, **kwargs)
   5872                         ymin = np.amin(m[m != 0])
   5873                         # filter out the 0 height bins
-> 5874                 ymin = max(ymin*0.9, minimum)
   5875                 ymin = min(ymin0, ymin)
   5876                 self.dataLim.intervaly = (ymin, ymax)

UnboundLocalError: local variable 'ymin' referenced before assignment