Product of an empty sequence

Alan G Isaac aisaac at american.edu
Thu Oct 19 08:07:51 CDT 2006


On Thu, 19 Oct 2006, Ivan Vilata i Balaguer apparently wrote: 
>>>> numpy.prod(()) 
> 1.0
> Wouldn't be 0.0 a more natural answer?

I think it must be 1 or a TypeError.  E.g.,
http://docs.python.org/lib/built-in-funcs.html#reduce
reduce(function, sequence[, initializer])
    Apply function of two arguments cumulatively to the 
    items of sequence, from left to right, so as to reduce 
    the sequence to a single value. For example, 
    reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates 
    ((((1+2)+3)+4)+5). The left argument, x, is the 
    accumulated value and the right argument, y, is the 
    update value from the sequence. If the optional 
    initializer is present, it is placed before the items of 
    the sequence in the calculation, and serves as a default 
    when the sequence is empty. If initializer is not given 
    and sequence contains only one item, the first item is 
    returned.

hth,
Alan Isaac
(just a user)



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