Need help in understanding a python code

[silverburgh.meryl]

Hi,

I am trying to understand the following line:
# a is an integer array

max([(sum(a[j:i]), (j,i))

Can you please tell me what that means,
I think sum(a[j:i] means find the some from a[j] to a[i]
But what is the meaning of the part (j,i)?

[John Machin]

On Nov 16, 11:04*pm, Steven D'Aprano <st...@REMOVE-THIS-
cybersource.com .auwrote:

On Sun, 16 Nov 2008 02:41:03 -0800, John Machin wrote:

On Nov 16, 9:31*pm, Steven D'Aprano <st...@REMOVE-THIS-
cybersource.com .auwrote:

On Sun, 16 Nov 2008 01:50:16 -0800, John Machin wrote:
def A(w, v, i,j):
* * if i == 0 or j == 0: return 0
* * if w[i-1] j: *return A(w, v, i-1, j) if w[i-1] <= j:return
* * max(A(w,v, i-1, j), v[i-1] +
* * * A(w,v, i-1, j - w[i-1]))
I am reading this blog

>http://20bits.com/articles/introduct...c-programming/

I suggest that you don't bother reading a blog written by somebody
who (presumably consciously) keyed in that "if w[i-1] <= j: " above.

That is a translation of standard terminology for a hybrid function.
Mathematics doesn't have an "else", so you write hybrid functions by
enumerating each branch as an if.

An else is not required.
* * if w[i-1] j:
* * * *return A(w, v, i-1, j)
* * return max(A(w,v, i-1, j), v[i-1] + A(w,v, i-1, j - w[i-1]))

Which is also not valid terminology for hybrid functions.

I couldn't care less. It's valid and efficient (compared to the
original) Python.

While it's not especially good Python technique, it's a perfectly
idiomatic mathematical expression, and shouldn't be the basis for
dismissing an entire blog.

He's meant to be writing Python code, not mathematical expressions.

And he's written Python code. Perfectly valid Python code. Just because
it is not what you consider to be idiomatic Python code isn't a good
reason to dismiss his entire blog.

What you've done is rather like me saying that because you failed to use
a colon after "required", and therefore haven't written what *I* consider
good English style, not only is your specific post best avoided, but
*all* your posts should be avoided. I trust you understand the logical
fallacy I would be making, which you have already made.

Nothing to do with style. It was the screaming inefficiency of:
if non_trivial_con dition: return x
if not non_trivial_con dition: return y
that fired me up.

http://en.wikipedia.org/wiki/Style_o...stance_fallacy

Quoted Wikipedia -instant disqualificatio n -you lose. Good night.

[George Sakkis]

On Nov 16, 7:34*am, John Machin <sjmac...@lexic on.netwrote:

On Nov 16, 11:04*pm, Steven D'Aprano <st...@REMOVE-THIS-

http://en.wikipedia.org/wiki/Style_o...stance_fallacy

Quoted Wikipedia -instant disqualificatio n -you lose. Good night.

When quoting wikipedia became the new Godwin's law ?? :)

George

[alex23]

On Nov 17, 5:26*am, George Sakkis <george.sak...@ gmail.comwrote:

When quoting wikipedia became the new Godwin's law ?? :)

Probably at the point the editors started becoming revisionists and
culling anything they didn't consider notable enough.

[Matt Nordhoff]

Benjamin Kaplan wrote:

If you really believe that, you haven't been following this list long
enough. Every terminology dispute always includes at least 1 Wikipedia
link.

Also, you might want to look at this study:
http://news.cnet.com/2100-1038_3-5997332.html

That study has been disputed; see the links at the top of
<http://en.wikipedia.or g/wiki/Reliability_of_ Wikipedia>.

/me ducks
--

[alex23]

On Nov 17, 11:40*am, Matt Nordhoff <mnordh...@matt nordhoff.comwro te:

That study has been disputed; see the links at the top of
<http://en.wikipedia.or g/wiki/Reliability_of_ Wikipedia>.

Now, if there was any independent refutation of the original study
that isn't based on Britannica's - not that I'm outright accusing them
of any bias here :) - that might make a reasonable disputation...

[Steven D'Aprano]

On Sun, 16 Nov 2008 04:34:40 -0800, John Machin wrote:

Nothing to do with style. It was the screaming inefficiency of:
if non_trivial_con dition: return x
if not non_trivial_con dition: return y
that fired me up.

"Screaming inefficiency"?

Try "micro-optimization". The difference in execution time between "if
x... if not x..." versus "if x... else..." on my slow, underpowered
machine is about 10**-8 seconds. If that's your idea of "screaming
inefficiency" I can't understand why you're programming in Python in the
first place.

Of course, if x is an expensive function call (say, a network lookup or
database query rather than a relatively cheap list indexing operation)
then the more readable, Pythonic solution will also be significantly
faster. There's no doubt that it should be preferred -- I'm not defending
it, as such, just pointing out the over-reaction of dismissing what is a
generally well-written and thought-out article on the basis of a
triviality.

>http://en.wikipedia.org/wiki/Style_o...stance_fallacy

Quoted Wikipedia -instant disqualificatio n -you lose. Good night.

Oh gosh, well, you've certainly proven your case, how could I be so
stupid? My apology for thinking that you were acting like an arrogant,
bad-tempered dick. I don't know *what* I was thinking.

--
Steven
who would link to Wikipedia for the definition of sarcasm except I've
already lost once in this thread and that's enough.