On 12/20/17 5:05 AM, Paul Moore wrote:
Well here is some code I wrote recently to build a histogram over a weighted graph, before becoming aware that Counter existed (score is a float here):
from collections import defaultdict
total_score_by_depth = defaultdict(float) total_items_by_depth = defaultdict(int) num_nodes_by_score = defaultdict(int) num_nodes_by_log_score = defaultdict(int) num_edges_by_score = defaultdict(int) for state in iter_graph_components(): try: # There is probably some overlap here ak = state['ak'] _, c = ak.score_paths(max_depth=15) for edge in state['graph'].edges: num_edges_by_score[np.ceil(20.0 * edge.score) / 20.0] += 1 for node in c.nodes: total_score_by_depth[node.depth] += node.score total_items_by_depth[node.depth] += 1 num_nodes_by_score[np.ceil(20.0 * node.score) / 20.0] += 1 num_nodes_by_log_score[np.ceil(-np.log10(node.score))] += 1 num_nodes_by_score[0.0] += len(state['graph'].nodes) - len(c.nodes) num_nodes_by_log_score[100.0] += len(state['graph'].nodes) - len(c.nodes) except MemoryError: print("Skipped massive.")
Without going too much into what this does, note that I could replace the other defaultdicts with Counters, but I can't do the same thing with a total_score_by_depth, at least not without violating the API. Hmm, OK. I can't see any huge benefit from switching to a Counter,
On 20 December 2017 at 03:09, Joel Croteau <jcroteau@gmail.com> wrote: though. You're not using any features of a Counter that aren't shared by a defaultdict, nor is there any code here that could be simplified or replaced by using such features...
I would suggest that with a name like Counter, treating a class like a Counter should be the more common use case. If it's meant to be a multiset, we should call it a Multiset. Personally, I consider "counting" to be something we do with integers (whole numbers), not with floats. So for me the name Counter clearly implies an integer. Multiset would be a reasonable alternative name, but Python has a tradition of using "natural language" names over "computer science" names, so I'm not surprised Counter was chosen instead.
I guess it's ultimately a matter of opinion whether a float-based Counter is a natural extension or not.
One thing to note is that Counter supports negative numbers, so we are already outside the natural numbers :) Python 3.6.4 (default, Dec 19 2017, 08:11:42) >>> from collections import Counter >>> c = Counter(a=4, b=2, c=0, d=-2) >>> d = Counter(a=1, b=2, c=3, d=4) >>> c.subtract(d) >>> c Counter({'a': 3, 'b': 0, 'c': -3, 'd': -6}) >>> list(c.elements()) ['a', 'a', 'a'] --Ned.