Style - was Re: numpy.repeat TypeError: array cannot be safely cast to required type

Tim Hochberg tim.hochberg at
Sat Nov 4 14:23:11 CST 2006

Colin J. Williams wrote:
> Tim Hochberg wrote:
> [snip]
>> A style note: please use the named dtypes (int32, uint32, etc) rather 
>> than the old-style letter codes; the former is much clearer. The answer 
>> to your question might  have been immediately apparent had you been 
>> using named dtypes.
> +1
>>  Personally, I'd also prefer people use the "ones([n])" syntax instead 
>> of the I-wish-it-were-deprecated-but-it's-too-much-to-hope-for "ones(n)" 
>> syntax.  T
>> -tim
> Could you elaborate please?
Sure. The general form of the zeros function, and several others[1], is:

    zeros(shape, dtype)

 Here 'shape' is a sequence of one sort or another. There's also a 
second form that's applicable only to one dimensional arrays:

    zeros(length, dtype)

Where length is an integer. I don't recall if this is a historical 
legacy or is intended as a convenience function or a bit of both. Either 
way, the result is that there are two ways to spell "give me a 1D array 
of zeros with a given length and dtype":

    zeros([length], dtype)


    zeros(length, dtype)

I have two issues with having this second spelling. First, it's one more 
thing to remember. Whenever I see the scalar spelling I have to use a 
little bit extra of my limited brainpower to remember that it is not in 
fact a typo, but is instead a shortcut. The second issue is pedagogical. 
If people are initially exposed to the first form, the extension to 
multiple dimensions is straightforward. They'll probably guess the 
correct way right off the bat, and if not, they'll get it right away 
when it's explained. On the other hand, if they are initially exposed to 
the second form, the multidimensional form is far from obvious. In 
addition, they'll probably spend a long time thinking that the 
one-dimensional way is the normal way, but that we have to jump through 
weird hoops to get multidimensional arrays to work. That's bad 
propaganda for numpy. This all seems like a rather large price to pay to 
avoid typing the occasional pair of brackets.

That's my two cents. Just say not to form #2.


... [1] Yes, I'm neglecting the order parameter; I don't think it 
matters for this discussion.

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