On Fri, Sep 26, 2008 at 7:22 AM, David Di Biase <[EMAIL PROTECTED]> wrote: > Hi Chris, > > Yeah I hear you on point A. but this the specification I was given, so I > have to follow it unfortunately. I've also been restricted and not allowed > to use any other packages. I was using NumPy earlier (should have mentioned > that) but I was wondering if there was a simpler way. Is NumPy technically > even faster than just iterating and modifying the list directly? > > Also if I'm creating an array then making it,
Uh, this part of your sentence doesn't quite make sense... > why not just do a temporary > sort and capture the first and last values? Is this method you've provided > supposed to be faster? Well, unless you're going to use the rest of the sorted values at some point in your program and since you have a large quantity of data, yes, my way ought to be faster. Sorting the list is O(N*log(N)) while running max and min over the list is only O(N). Regards, Chris > > Dave > > On Fri, Sep 26, 2008 at 12:42 AM, Chris Rebert <[EMAIL PROTECTED]> wrote: >> >> On Thu, Sep 25, 2008 at 8:57 PM, David Di Biase <[EMAIL PROTECTED]> >> wrote: >> > I have a list with about 1000-1500 sub-lists which look like so: >> > list[-0.28817955213290786, 3.6693631467403929, 'H', 31.31225233035784]] >> > >> > The first and second values are Angstrom units specifying the location >> > of a >> > particle. What I'd like to do is determine the distance between the >> > smallest >> > and largest value in the arrays first position 0. I tried reading the >> > manual >> > for this but I don't see how it applies key or any of those other >> > commands >> > to the function. I could easily write a sort to do this and capture the >> > first and last spots, but why do that when I can use max and min (if I >> > can >> > actually do that...). >> >> A. You should probably be using objects rather than arrays to >> represent your datapoints, so that they're more structured and it's >> more apparent what the values mean. >> >> B. Assuming by "distance" you meant "difference" and/or that the >> distance is only in 1 dimension: >> >> from operator import itemgetter >> firsts = map(itemgetter(0), main_list) >> distance = max(firsts) - min(firsts) >> >> > >> > So you wonderful Python gods, lay some knowledge on me. please? lol... >> > >> > while I'm at it, is there a way to modify an entire list without having >> > to >> > produce a whole new one? For example now say I want to modify list[0] >> > and >> > multiply it by some value. From what I understand previous version of >> > Python >> > allowed lists to be multiplied like matrices...now apparently it just >> > replicates the list. :-/ shucks... >> >> You just have to apply the transform to each list element individually >> (also, you might consider using NumPy [http://numpy.scipy.org/] if >> you're doing a lot of matrix manipulation): >> >> for lst in main_list: >> lst[0] *= some_value >> >> Regards, >> Chris >> >> > >> > The first question would be useful to know, but the second question I do >> > quite a bit of and the "best practice" would be really great to know! >> > >> > Thanks in advanced! >> > >> > -- >> > http://mail.python.org/mailman/listinfo/python-list >> > >> -- >> Follow the path of the Iguana... >> http://rebertia.com > > -- Follow the path of the Iguana... http://rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
