[Numpy-discussion] fromiter shape argument -- was Re: For loop tips

[Tim Hochberg]

Torgil Svensson wrote:
>>    return uL,asmatrix(fromiter((idx[x] for x in L),dtype=int))
>>     
>
> Is it possible for fromiter to take an optional shape (or count)
> argument in addition to the dtype argument? 
Yes. fromiter(iterable, dtype, count) works.

> If both is given it could
> preallocate memory and we only have to iterate over L once.
>   
Regardless, L is only iterated over once. In general you can't rewind 
iterators, so that's a requirement. This is accomplished by doing 
successive overallocation similar to the way appending to a list is 
handled. By specifying the count up front you save a bunch of reallocs, 
but no iteration.

-tim



> //Torgil
>
> On 8/29/06, Keith Goodman <kwgoodman at gmail.com> wrote:
>   
>> On 8/29/06, Torgil Svensson <torgil.svensson at gmail.com> wrote:
>>     
>>> something like this?
>>>
>>> def list2index(L):
>>>    uL=sorted(set(L))
>>>    idx=dict((y,x) for x,y in enumerate(uL))
>>>    return uL,asmatrix(fromiter((idx[x] for x in L),dtype=int))
>>>       
>> Wow. That's amazing. Thank you.
>>
>> -------------------------------------------------------------------------
>> Using Tomcat but need to do more? Need to support web services, security?
>> Get stuff done quickly with pre-integrated technology to make your job easier
>> Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
>> http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
>> _______________________________________________
>> Numpy-discussion mailing list
>> Numpy-discussion at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/numpy-discussion
>>
>>     
>
> -------------------------------------------------------------------------
> Using Tomcat but need to do more? Need to support web services, security?
> Get stuff done quickly with pre-integrated technology to make your job easier
> Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
> http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> _______________________________________________
> Numpy-discussion mailing list
> Numpy-discussion at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/numpy-discussion
>
>
>