模拟多关键字字典
multi_key_dict不支持同时使用多个关键字进行__getitem__()操作...
(例如：d["red", "green"])
一个多键可以使用
tuple 或
set 键模拟。如果顺序不重要，
set 似乎是最好的选择（实际上是可哈希的
frozen set，所以 [
"red", "blue"] 和
["blue", "red"] 是相同的）。
模拟多值字典
Multi values 是使用某些数据类型固有的，它可以是一个方便索引的
任何存储元素。标准的
dict 应该提供这个功能。
非确定性
使用由规则和假设定义的概率分布1，使用 python文档中的此处配方 进行非确定性选择。
MultiKeyMultiValNonDeterministicDict 类
多么奇怪的名字。 \o/-太棒了！
该类接受多个键，定义了一个由多个值组成的概率规则集。在创建项(
__setitem__())时，所有键的值的概率都被预先计算出来，适用于所有键组合
1。在访问项(
__getitem__())时，会选择预先计算好的概率分布，并根据随机加权选择进行评估。
定义
import random
import operator
import bisect
import itertools
def accumulate(iterable, func=operator.add):
'Return running totals'
it = iter(iterable)
try:
total = next(it)
except StopIteration:
return
yield total
for element in it:
total = func(total, element)
yield total
class MultiKeyMultiValNonDeterministicDict(dict):
def key_combinations(self, keys):
"""get all combinations of keys"""
return [frozenset(subset) for L in range(0, len(keys)+1) for subset in itertools.combinations(keys, L)]
def multi_val_rule_prob(self, rules, rule):
"""
assign probabilities for each value,
spreading undefined result probabilities
uniformly over the leftover results not defined by rule.
"""
all_results = set([result for result_probs in rules.values() for result in result_probs])
prob = rules[rule]
leftover_prob = 1.0 - sum([x for x in prob.values()])
leftover_results = len(all_results) - len(prob)
for result in all_results:
if result not in prob:
prob[result] = leftover_prob/leftover_results
return prob
def multi_key_rule_prob(self, key, val):
"""
assign probability distributions for every combination of keys,
using the default for combinations not defined in rule set
"""
combo_probs = {}
for combo in self.key_combinations(key):
if combo in val:
result_probs = self.multi_val_rule_prob(val, combo).items()
else:
result_probs = self.multi_val_rule_prob(val, frozenset([])).items()
combo_probs[combo] = result_probs
return combo_probs
def weighted_random_choice(self, weighted_choices):
"""make choice from weighted distribution"""
choices, weights = zip(*weighted_choices)
cumdist = list(accumulate(weights))
return choices[bisect.bisect(cumdist, random.random() * cumdist[-1])]
def __setitem__(self, key, val):
"""
set item in dictionary,
assigns values to keys with precomputed probability distributions
"""
precompute_val_probs = self.multi_key_rule_prob(key, val)
dict.__setitem__(self, frozenset(key), precompute_val_probs)
def __getitem__(self, key):
"""
get item from dictionary,
randomly select value based on rule probability
"""
key = frozenset([key]) if isinstance(key, str) else frozenset(key)
val = None
weighted_val = None
if key in self.keys():
val = dict.__getitem__(self, key)
weighted_val = val[key]
else:
for k in self.keys():
if key.issubset(k):
val = dict.__getitem__(self, k)
weighted_val = val[key]
if weighted_val:
prob_results = self.weighted_random_choice(weighted_val)
else:
prob_results = None
return prob_results
使用方法
d = MultiKeyMultiValNonDeterministicDict()
d["red","blue","green"] = {
# {rule_set} : {result: probability}
frozenset(["red", "green"]): {"ballon": 0.8},
frozenset(["blue"]): {"toy": 0.15},
frozenset([]): {"car": 0.05}
}
测试
检查概率
N = 10000
red_green_test = {'car':0.0, 'toy':0.0, 'ballon':0.0}
red_blue_test = {'car':0.0, 'toy':0.0, 'ballon':0.0}
blue_test = {'car':0.0, 'toy':0.0, 'ballon':0.0}
red_blue_green_test = {'car':0.0, 'toy':0.0, 'ballon':0.0}
default_test = {'car':0.0, 'toy':0.0, 'ballon':0.0}
for _ in xrange(N):
red_green_test[d["red","green"]] += 1.0
red_blue_test[d["red","blue"]] += 1.0
blue_test[d["blue"]] += 1.0
default_test[d["green"]] += 1.0
red_blue_green_test[d["red","blue","green"]] += 1.0
print 'red,green test =', ' '.join('{0}: {1:05.2f}%'.format(key, 100.0*val/N) for key, val in red_green_test.items())
print 'red,blue test =', ' '.join('{0}: {1:05.2f}%'.format(key, 100.0*val/N) for key, val in red_blue_test.items())
print 'blue test =', ' '.join('{0}: {1:05.2f}%'.format(key, 100.0*val/N) for key, val in blue_test.items())
print 'default test =', ' '.join('{0}: {1:05.2f}%'.format(key, 100.0*val/N) for key, val in default_test.items())
print 'red,blue,green test =', ' '.join('{0}: {1:05.2f}%'.format(key, 100.0*val/N) for key, val in red_blue_green_test.items())
red,green test = car: 09.89% toy: 10.06% ballon: 80.05%
red,blue test = car: 05.30% toy: 47.71% ballon: 46.99%
blue test = car: 41.69% toy: 15.02% ballon: 43.29%
default test = car: 05.03% toy: 47.16% ballon: 47.81%
red,blue,green test = car: 04.85% toy: 49.20% ballon: 45.95%
概率符合规则！
注脚
Distribution Assumption
Since the rule set is not fully defined, assumptions are made about the probability distributions, most of this is done in multi_val_rule_prob(). Basically any undefined probability will be spread uniformly over the remaining values. This is done for all combinations of keys, and creates a generalized key interface for the random weighted selection.
Given the example rule set
d["red","blue","green"] = {
# {rule_set} : {result: probability}
frozenset(["red", "green"]): {"ballon": 0.8},
frozenset(["blue"]): {"toy": 0.15},
frozenset([]): {"car": 0.05}
}
this will create the following distributions
'red' = [('car', 0.050), ('toy', 0.475), ('ballon', 0.475)]
'green' = [('car', 0.050), ('toy', 0.475), ('ballon', 0.475)]
'blue' = [('car', 0.425), ('toy', 0.150), ('ballon', 0.425)]
'blue,red' = [('car', 0.050), ('toy', 0.475), ('ballon', 0.475)]
'green,red' = [('car', 0.098), ('toy', 0.098), ('ballon', 0.800)]
'blue,green' = [('car', 0.050), ('toy', 0.475), ('ballon', 0.475)]
'blue,green,red'= [('car', 0.050), ('toy', 0.475), ('ballon', 0.475)]
default = [('car', 0.050), ('toy', 0.475), ('ballon', 0.475)]
If this is incorrect, please advise.
d['red']==d['green']是什么意思？这是因为您之前查找过包含这两个键的多键吗？我理解您的问题是指d['red'] != d['red']不一定成立... - Andy Haydend['red','blue','green']= "baloon" or "car" or "toy"，并为这些物品设置了概率。如果执行d['red']='ball'会发生什么？ - dawg