list comprehension question

[rusi]

On Oct 17, 7:14 am, Dave Angel <d... at davea.name> wrote:
> On 10/16/2012 09:54 PM, Kevin Anthony wrote:
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> > I've been teaching myself list comprehension, and i've run across something
> > i'm not able to convert.
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> > here's the original code for matrix multiplcation
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> > retmatrix = Matrix(self.__row,other.__col)
> > for m in range(0,retmatrix.__row):
> >     for n in range(0,retmatrix.__col):
> >         product = 0
> >         for p in range(1,self.__col+1):
> >             product += (self.__matrix[m][p] * other.__matrix[p][n])
> >         retmatrix.__matrix[m][n] = product
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> > Here is what i have so far:
> > retmatrix.__matrix = [[ product = product + (self.__matrix[m][p]*
> > other.__matrix[p][n])
> >                  if product else self.__matrix[m][p]* other.__matrix[p][n])
> >                  for p in range(0,self.col)
> >                  for n in range(0,self.col)]
> >                  for m in range(0,self.__row)]
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> > But i know that isn't correct, can someone nudge my in the right direction?
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> The biggest thing to learn about list comprehensions is when not to use
> them.  I can't imagine how your latter version (even if correct) is
> clearer than the first.
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> --
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> DaveA

Try rewriting using dot

from operator import mul
def dot(p,q):
  return reduce(mul, [x*y for x,y in zip(p,q)])  # the [] can become
()

and avoiding object-orientation (at least to start with)