Hi there, I've been using Numpy for several years and appreciate it very much. The following minimal code has been tried on Python 3.4 and 3.5, with Numpy 1.8 and Numpy 1.11, respectively. I want to temporarily change the way that a Numpy array is printed, then change it back. import numpy as np a = np.random.random((4,3)) print(a, "\n") opt = np.get_printoptions() np.set_printoptions(precision = 3, suppress = True) print(a, "\n") np.set_printoptions(opt) print(a, "\n\nDone.\n") Here is the traceback: Traceback (most recent call last): File "set_printoptions test.py", line 11, in <module> print(a, "\n\nDone.\n") File "/usr/lib/python3/dist-packages/numpy/core/numeric.py", line 1615, in array_str return array2string(a, max_line_width, precision, suppress_small, ' ', "", str) File "/usr/lib/python3/dist-packages/numpy/core/arrayprint.py", line 454, in array2string separator, prefix, formatter=formatter) File "/usr/lib/python3/dist-packages/numpy/core/arrayprint.py", line 328, in _array2string _summaryEdgeItems, summary_insert)[:-1] File "/usr/lib/python3/dist-packages/numpy/core/arrayprint.py", line 523, in _formatArray summary_insert) File "/usr/lib/python3/dist-packages/numpy/core/arrayprint.py", line 497, in _formatArray word = format_function(a[-i]) + separator File "/usr/lib/python3/dist-packages/numpy/core/arrayprint.py", line 616, in __call__ s = self.format % x AttributeError: 'FloatFormat' object has no attribute 'format' It took me a while to discover the bug, on the second to last line. That line should read: np.set_printoptions(**opt) This unpacks the dictionary, opt, which was retrieved earlier in the program with the call to get_printoptions. I am wondering why set_printoptions would accept the dictionary as a single argument. Shouldn't that raise a TypeError or something? The AttributeError that is raised the next time that one attempts to print a numpy array is remote from the problem, and thus rather uninformative, which is why I did not immediately diagnose my error. Should this be considered a Numpy bug, or is there some reason that set_printoptions would legitimately need to accept a dictionary as a single argument? -- *John J. Ladasky Jr., Ph.D.* *Research Scientist* *International Technological University* *2711 N. First St, San Jose, CA 95134 USA*