python - 函数 python 调用后未返回内存

Question

我有一个函数可以通过构建图表来解析句子。但是 Python 保留在该函数调用期间分配的任何内存。也就是说，我愿意

best = translate(sentence, grammar)

不知何故，我的内存力上升并保持不变。这是函数:

from string import join
from heapq import nsmallest, heappush
from collections import defaultdict

MAX_TRANSLATIONS=4 # or choose something else

def translate(f, g):
    words = f.split()
    chart = {}
    for col in range(len(words)):
        for row in reversed(range(0,col+1)):
            # get rules for this subspan                                        
            rules = g[join(words[row:col+1], ' ')]
            # ensure there's at least one rule on the diagonal                  
            if not rules and row==col:
                rules=[(0.0, join(words[row:col+1]))]
            # pick up rules below & to the left                                 
            for k in range(row,col):
                if (row,k) and (k+1,col) in chart:
                    for (w1, e1) in chart[row, k]:
                        for (w2, e2) in chart[k+1,col]:
                            heappush(rules, (w1+w2, e1+' '+e2))
            # add all rules to chart                                            
            chart[row,col] = nsmallest(MAX_TRANSLATIONS, rules)
    (w, best) = chart[0, len(words)-1][0]
    return best

g = defaultdict(list)
g['cela'] = [(8.28, 'this'), (11.21, 'it'), (11.57, 'that'), (15.26, 'this ,')]
g['est'] = [(2.69, 'is'), (10.21, 'is ,'), (11.15, 'has'), (11.28, ', is')]
g['difficile'] = [(2.01, 'difficult'), (10.08, 'hard'), (10.19, 'difficult ,'), (10.57, 'a difficult')]

sentence = "cela est difficile"
best = translate(sentence, g)

我在 OS X 上使用 Python 2.7。

Answer 1

在该函数中，您将rules 设置为grammar 的一个元素； rules 然后引用该元素，它是一个列表。然后，您使用 heappush 将项目添加到 rules，这(因为列表是可变的)意味着 grammar 保留通过该列表推送的值。如果您不想发生这种情况，请使用 copy在 translate 开头的语法上分配 rules 或 deepcopy 时。请注意，即使您将列表复制到 rules，每次您检索缺少键的元素时，语法都会记录一个空列表。