sequence multiplied by -1

Carl Banks pavlovevidence at
Tue Oct 5 01:50:39 CEST 2010

On Oct 4, 3:09 pm, Gregory Ewing <greg.ew... at> wrote:
> Carl Banks wrote:
> > Numpy uses + for elementwise addition, and a function
> > called concatenate for concatenation.  If Python lists used a separate
> > concatenation operator, then Numpy arrays could use that for
> > concatenation.
> Actually it couldn't, except for the special case of
> concatenating along the first axis.

IOW, it could.

> The concatenate()
> function allows specifying an axis.

Take the example of the pow() function which allows several arguments,
but that doesn't prevent there from being a ** operator.

> There's also the problem that applying a concatenation
> operator to a numpy array of Python sequences would be
> ambiguous -- does it mean concatenating the arrays, or
> elementwise concatenation of their contents?

It means concatenating the arrays.  The operator wouldn't be
elementwise for any other array; there is no argument to make it that
way for arrays of sequences.  Non problem.

Carl Banks

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