list comprehension return a list and sum over in loop

[Peter Otten]

KK Sasa wrote:

> Peter Otten於 2014年12月12日星期五UTC+8下午8時32分55秒寫道：
>> Jussi Piitulainen wrote:
>> 
>> > KK Sasa writes:
>> > 
>> >> def p(x,t,point,z,obs):
>> >>     d = x[0]
>> >>     tau = [0]+[x[1:point]]
>> >>     a = x[point:len(x)]
>> >>     at = sum(i*j for i, j in zip(a, t))
>> >>     nu = [exp(z[k]*(at-d)-sum(tau[k])) for k in xrange(point)]
>> >>     de = sum(nu, axis=0)
>> >>     probability = [nu[k]/de for k in xrange(point)]
>> >>     return probability[obs]
>> > 
>> > I must be blind, but this looks like computing a whole probability
>> > distribution and then throwing almost all of it away.
>> > 
>> > Can't this just return nu[obs]/de?
>> > 
>> > The expression for tau also seems weird to me. Isn't it equivalent to
>> > [0, x[1:point]], a two-element list with the second element a list?
>> > How can sum(tau[k]) work at all then, for any k > 1?
>> 
>> Also, after adding
>> 
>> from numpy.random import seed
>> 
>> to the code I run into the next problem:
>> 
>> Traceback (most recent call last):
>>   File "hessian.py", line 34, in <module>
>>     re = [d2(x,t[k],2,z,1) for k in range_people]
>>   File "/home/petto/.local/lib/python2.7/site-packages/ad/__init__.py",
>>   line
>> 1114, in hess
>>     return func(xa, *args).hessian([xa])
>>   File "hessian.py", line 26, in p
>>     nu = [exp(z[k]*(at-d)-sum(tau[k])) for k in xrange(point)]
>> TypeError: 'int' object is not iterable
>> 
>> OP: Optimizations only make sense when you can start from a known-good
>> base. You should sort out the logic of your problem (we probably can't
>> help you with that), then fix the bugs in your code and only then revisit
>> the "speed issue".
> 
> I have no idea why you added "from numpy.random import seed" to this
> syntax. Even I added that, my python didn't complain any bugs inside.
> Maybe your ad package was not be installed correctly?

It may be a version issue. I'm using

>>> import ad, numpy
>>> ad.__version__
'1.2.2'
>>> numpy.__version__
'1.9.1'

Or are you using an environment that does some imports automatically?