This could work: l = [0,0,1,2,1,0,0] indexes, values = zip(*((index,value) for index,value in enumerate(l) if value != 0))
But I guess it would be a little less cryptic (and maybe a lot more efficient) if there were an unzip function instead of using the zip(*sequence) trick. I think a more readable way would be: indexes = [index for index,value in enumerate(l) if value != 0] values = [value for value in l if value != 0] Cheers. -- Luis Zarrabeitia Facultad de Matemática y Computación, UH http://profesores.matcom.uh.cu/~kyrie Quoting Benjamin Goudey <[EMAIL PROTECTED]>: > I have a very large list of integers representing data needed for a > histogram that I'm going to plot using pylab. However, most of these > values (85%-95%) are zero and I would like to remove them to reduce > the amount of memory I'm using and save time when it comes to plotting > the data. To do this, I'm trying to find the best way to remove all of > the zero values and produce a list of indices of where the non-zero > values used to be. > > For example, if my original list is [0,0,1,2,1,0,0] I would like to > produce the lists [1,2,1] (the non zero values) and [2,3,4] (indices > of where the non-zero values used to be). Removing non-zero values is > very easy but determining the indicies is where I'm having difficulty. > > Thanks in advance for any help > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
