import numpy print numpy.__version__ for s in range(1864100, 1864200): if numpy.ones((s, 9), numpy.float32).sum()!= s*9: print '\nbroke', s break else: print '\r',s, C:\temp>python np_sum.py 1.8.0b2 1864135 broke 1864136 import numpy print numpy.__version__ for s in range(1864130*9, 1864135*9): if numpy.ones((s, 1), numpy.float32).sum()!= s: print '\nbroke', s break else: print '\r',s, C:\temp>python np_sum.py 1.8.0b2 16777214