Prev: Book review / advise
Next: Google Adsense Account Approval With In 4 Hours
From: Neil Webster on 22 Jun 2010 10:06
Hi all,

I've got a simple problem but it's defeated me and I was wondering if
somebody could point out where I'm going wrong or offer an alternative
solution to the problem?

I have a list of lists such as [[a,2,3,4],[b,10,11,12], [a,2,3,4]]. I
need to combine the two lists that have the same first character in
this example 'a'. In reality there are 656 lists within the list.

My attempt so far is:
L = [[a,2,3,4],[b,10,11,12], [a,2,3,4]]
d = []
z = 1
while z <= len(L):
for a in L:
if L.count(a[0]) > 1:
d.append(a[2:])

summed = [sum(pair) for pair in zip(d[0], d[1])]
z = z+1
print summed

Any pointers more than welcome.

Thanks all.

From: James Mills on 22 Jun 2010 10:30
On Wed, Jun 23, 2010 at 12:06 AM, Neil Webster <nswebster(a)gmail.com> wrote:
> I've got a simple problem but it's defeated me and I was wondering if
> somebody could point out where I'm going wrong or offer an alternative
> solution to the problem?

Is this a hypothetical/mathematical problem of sorts ?
If so, do you have the actual problem description ?

It's often better to come up with a different (perhaps better)
solution without looking at someone else's :)

--james


--
--
-- "Problems are solved by method"
From: Mark Lawrence on 22 Jun 2010 10:40
On 22/06/2010 15:06, Neil Webster wrote:
> Hi all,
>
> I've got a simple problem but it's defeated me and I was wondering if
> somebody could point out where I'm going wrong or offer an alternative
> solution to the problem?
>
> I have a list of lists such as [[a,2,3,4],[b,10,11,12], [a,2,3,4]]. I
> need to combine the two lists that have the same first character in
> this example 'a'. In reality there are 656 lists within the list.
>
> My attempt so far is:
> L = [[a,2,3,4],[b,10,11,12], [a,2,3,4]]
> d = []
> z = 1
> while z<= len(L):
> for a in L:
> if L.count(a[0])> 1:
> d.append(a[2:])
>
> summed = [sum(pair) for pair in zip(d[0], d[1])]
> z = z+1
> print summed
>
> Any pointers more than welcome.
>
> Thanks all.
>

My simplistic approach.

Sort the list (this happens in place).
Use the itertools groupby function to place everything together, see
http://docs.python.org/library/itertools.html?highlight=groupby#itertools.groupby
Combine the lists in the groups.

HTH.

Mark Lawrence.

From: Bruno Desthuilliers on 22 Jun 2010 11:38
Neil Webster a �crit :
> Hi all,
>
> I've got a simple problem but it's defeated me and I was wondering if
> somebody could point out where I'm going wrong

1/ not posting working code (got a NameError)
2/ not posting the expected output
3/ not posting the actual output

> or offer an alternative
> solution to the problem?

When you'll have fixed the 3 problems listed above !-)

(snip broken code)
From: Neil Webster on 24 Jun 2010 05:21
Thanks for the help so far.

The background to the problem is that the lists come from reading a
dbf file. The code that I am trying to write is to merge lines of the
dbf based on the first column. So in my example there would be three
lines:
a 2 3 4
b 10 11 12
a 2 3 4

The expected output from the above example lines would be:
a 4 6 8
b 10 11 12

... and the lines are read as: [[a,2,3,4],[b,10,11,12], [a,2,3,4]]

In response to not posting working code or actual inputs, ummm, that's
why I am asking the question here.








On Jun 22, 4:38 pm, Bruno Desthuilliers <bruno.
42.desthuilli...(a)websiteburo.invalid> wrote:
> Neil Webster a crit :
>
> > Hi all,
>
> > I've got a simple problem but it's defeated me and I was wondering if
> > somebody could point out where I'm going wrong
>
> 1/ not posting working code (got a NameError)
> 2/ not posting the expected output
> 3/ not posting the actual output
>
> > or offer an alternative
> > solution to the problem?
>
> When you'll have fixed the 3 problems listed above !-)
>
> (snip broken code)

 |  Next  |  Last
Pages: 1 2
Prev: Book review / advise
Next: Google Adsense Account Approval With In 4 Hours