[EMAIL PROTECTED] wrote: > All, > > I can't seem to find an answer to this question anywhere, but I'm > still looking. My problem is I have a list of values like this: > > l = [0xF0, 1, 2, 3, 0xF0, 4, 5, 6, 0xF1, 7, 8, 0xF2, 9, 10, 11, 12, > 13, 0xF0, 14, 0xF1, 15] > > A value with bit 0x80 set delineates the start of a new packet of > information. What I want to do is to group the packets so that 1, 2, 3 > go with the 1st packet tagged 0xF0, 4 ,5, 6 go with the 2nd packet > tagged 0xF0, 7 & 8 go with the packet tagged 0xF1 and so on. The > length of the data associated with each tag can vary. I've already > written an algorithm to do this but I was wondering if some > combination of itertools functions could do the job faster? > > Here's what I've done and the expected output of the algorithm: > > def splitIntoGroups(data): > groups = [] > local = [] > > for value in data: > if 0x80 & value: > if len(local) > 0: > groups.append(local) > > local = [] > local.append(value) > else: > local.append(value) > > if len(local) > 0: > groups.append(local) > > return groups > > l = [0xF0, 1, 2, 3, 0xF0, 4, 5, 6, 0xF1, 7, 8, 0xF2, 9, 10, 11, 12, > 13, 0xF0, 14, 0xF1, 15] > > print splitIntoGroups(l) > > Desired result: > > [[240, 1, 2, 3], [240, 4, 5, 6], [241, 7, 8], [242, 9, 10, 11, 12, > 13], [240, 14], [241, 15]] > > Thanks, > > Dan McLeran >
Here's how I *would* do it: py> def doit(alist): ... ary = [] ... for i in alist: ... if 0xf0 & i: ... ary.append([i]) ... else: ... ary[-1].append(i) ... return [x for x in ary if x] ... py> doit(alist) [[240, 1, 2, 3], [240, 4, 5, 6], [241, 7, 8], [242, 9, 10, 11, 12, 13], [240, 14], [241, 15]] Here's an ugly way I wouldn't recommended (using itertools groupby): py> from itertools import groupby py> alist = [0xF0, 1, 2, 3, 0xF0, 4, 5, 6, ... 0xF1, 7, 8, 0xF2, 9, 10, 11, 12, 13, ... 0xF0, 14, 0xF1, 15] py> def doit(alist): ... i = (list(g) for k,g in groupby(alist, lambda x: 0xf0&x)) ... return [k for k in [j + i.next() for j in i] if len(k)>1] ... py> doit(alist) [[240, 1, 2, 3], [240, 4, 5, 6], [241, 7, 8], [242, 9, 10, 11, 12, 13], [240, 14], [241, 15]] James -- James Stroud UCLA-DOE Institute for Genomics and Proteomics Box 951570 Los Angeles, CA 90095 http://www.jamesstroud.com/ -- http://mail.python.org/mailman/listinfo/python-list
