[Python-ideas] Re: Python array multiplication for negative values should throw an error

[fjwillemsen--- via Python-ideas]

Thank you, that is a good point! I would expect a similar error message for 
multiplication with negative integers. 
A real-world example could be the scenario where I encountered this: arrays 
were consistently assumed to be NumPy arrays, but in some cases cached versions 
of these arrays would be loaded from a JSON file without casting them to a 
NumPy array. 
Because the function signatures all state NumPy arrays, I applied an array * -1 
operation before interpolation and other operations, in the expectation that 
this would yield the inverse of the elements instead of an empty list. It took 
me a while to find out that the problem was not in the interpolation or other 
operations following it, but in the array type. 
Of course, such bugs do not occur solely due to the lack of a raised errors on 
negative multiplication: in this case, a combination of a faulty assumption on 
the programmers' part and Python's lack of strict typing. However, raising an 
error on negative multiplication would immediately make it clear what is wrong, 
instead of hiding it.
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