Re: find minimum associated values
On Jan 26, 7:58 am, [EMAIL PROTECTED] wrote:
I find the first and third solutions simpler to read, and the first
solution requires less memory, it probably works quite well with
Psyco, and it's easy to translate to other languages (that is
important for programs you want to use for a lot of time or in
different situations), so I'd use the first solution.
The first solution, once one changes d = dict() to d = {}, is
quite free of any impediments to ease of reading, uses the minimum
necessary memory to build the required dict [and it's quite obvious by
inspection that this is so], and is the easiest to translate to
earlier versions of Python.
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Re: find minimum associated values
[EMAIL PROTECTED] wrote: I'd use the first solution. It can be speeded up a bit with a try/except: for k,v in kv: try: if d[k] v: d[k] = v except KeyError: d[k] = v Cheers, Alan Isaac -- http://mail.python.org/mailman/listinfo/python-list
Re: find minimum associated values
Alan Isaac wrote: #sort by id and then value kv_sorted = sorted(kv, key=lambda x: (id(x[0]),x[1])) #groupby: first element in each group is object and its min value d =dict( g.next() for k,g in groupby( kv_sorted, key=lambda x: x[0] ) ) Yes, that appears to be fastest and is pretty easy to read. On average. For the specified problem. ;-) -- http://mail.python.org/mailman/listinfo/python-list
Re: find minimum associated values
Steven Bethard wrote: [3rd approach] Seems pretty enough to me. ;-) I find it most attractive of the lot. But its costs would rise if the number of values per object were large. Anyway, I basically agree. Thanks, Alan -- http://mail.python.org/mailman/listinfo/python-list
Re: find minimum associated values
Alan Isaac wrote: I have a small set of objects associated with a larger set of values, and I want to map each object to its minimum associated value. The solutions below work, but I would like to see prettier solutions... [snip] # arbitrary setup keys = [Pass() for i in range(10)]*3 vals = [random.random() for i in range(30)] kv = zip(keys,vals) random.shuffle(kv) #OBJECTIVE: # find minimum val associated with each key in kv [snip] print method 3: defaultdict t=time.clock() d = defaultdict(list) for k,v in kv: d[k].append(v) for k in d: d[k] = min(d[k]) print time.clock()-t print d This is definitely the approach I'd use. Seems pretty enough to me. ;-) STeVe -- http://mail.python.org/mailman/listinfo/python-list
find minimum associated values
I have a small set of objects associated with a larger set of values, and I want to map each object to its minimum associated value. The solutions below work, but I would like to see prettier solutions... Thank you, Alan Isaac === import time, random from itertools import groupby from collections import defaultdict class Pass: pass # arbitrary setup keys = [Pass() for i in range(10)]*3 vals = [random.random() for i in range(30)] kv = zip(keys,vals) random.shuffle(kv) #OBJECTIVE: # find minimum val associated with each key in kv print method 1: brute force t=time.clock() d = dict() for k,v in kv: if k in d: if d[k] v: d[k] = v else: d[k] = v print time.clock()-t print d print print method 2: groupby t=time.clock() d = dict() kv_sorted = sorted(kv, key=lambda x: id(x[0])) for k, g in groupby( kv_sorted, key=lambda x: x[0] ): d[k] = min(gi[1] for gi in g) print time.clock()-t print d print print method 3: defaultdict t=time.clock() d = defaultdict(list) for k,v in kv: d[k].append(v) for k in d: d[k] = min(d[k]) print time.clock()-t print d -- http://mail.python.org/mailman/listinfo/python-list
Re: find minimum associated values
Alan Isaac [EMAIL PROTECTED] writes: print method 2: groupby t=time.clock() d = dict() kv_sorted = sorted(kv, key=lambda x: id(x[0])) How about something like: kv_sorted = sorted(kv, key=lambda x: (id(x[0]), x[1])) Now do your groupby and the first element of each group is the minimum for that group. -- http://mail.python.org/mailman/listinfo/python-list
Re: find minimum associated values
I find the first and third solutions simpler to read, and the first solution requires less memory, it probably works quite well with Psyco, and it's easy to translate to other languages (that is important for programs you want to use for a lot of time or in different situations), so I'd use the first solution. Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
Re: find minimum associated values
Paul Rubin wrote: How about something like: kv_sorted = sorted(kv, key=lambda x: (id(x[0]), x[1])) You mean like this? #sort by id and then value kv_sorted = sorted(kv, key=lambda x: (id(x[0]),x[1])) #groupby: first element in each group is object and its min value d =dict( g.next() for k,g in groupby( kv_sorted, key=lambda x: x[0] ) ) Yes, that appears to be fastest and is pretty easy to read. Thanks, Alan -- http://mail.python.org/mailman/listinfo/python-list
