添加单个字符以在 Counter 中添加键

Question

如果 Counter 对象的键的类型是 str，即：

我可以这样做：

>>> vocab_counter = Counter("the lazy fox jumps over the brown dog".split())

>>> vocab_counter  = Counter({k+u"\uE000":v for k,v in vocab_counter.items()})
>>> vocab_counter
Counter({'brown\ue000': 1,
         'dog\ue000': 1,
         'fox\ue000': 1,
         'jumps\ue000': 1,
         'lazy\ue000': 1,
         'over\ue000': 1,
         'the\ue000': 2})

什么是快速 and/or pythonic 方法来向所有键添加一个字符？

是不是只有上面的方法才能实现最终的计数器全部键都加字符？还有其他方法可以达到相同的目标吗？

Answer 1

更好的方法是在创建计数器对象之前添加该字符。您可以使用 Counter:

中的生成器表达式来完成此操作

In [15]: vocab_counter = Counter(w + u"\uE000" for w in "the lazy fox jumps over the brown dog".split())

In [16]: vocab_counter
Out[16]: Counter({'the\ue000': 2, 'fox\ue000': 1, 'dog\ue000': 1, 'jumps\ue000': 1, 'lazy\ue000': 1, 'over\ue000': 1, 'brown\ue000': 1})

如果在创建计数器之前无法修改单词，您可以覆盖 Counter 对象以添加特殊字符 during setting the values for keys.

Answer 2

我能想到的唯一其他优化方法是使用 Counter 的子类，在插入键时附加字符：

from collections import Counter


class CustomCounter(Counter):
    def __setitem__(self, key, value):
        if len(key) > 1 and not key.endswith(u"\uE000"):
            key += u"\uE000"
        super(CustomCounter, self).__setitem__(key, self.get(key, 0) + value)

演示：

>>> CustomCounter("the lazy fox jumps over the brown dog".split())
CustomCounter({u'the\ue000': 2, u'fox\ue000': 1, u'brown\ue000': 1, u'jumps\ue000': 1, u'dog\ue000': 1, u'over\ue000': 1, u'lazy\ue000': 1})
# With both args and kwargs 
>>> CustomCounter("the lazy fox jumps over the brown dog".split(), **{'the': 1, 'fox': 3})
CustomCounter({u'fox\ue000': 4, u'the\ue000': 3, u'brown\ue000': 1, u'jumps\ue000': 1, u'dog\ue000': 1, u'over\ue000': 1, u'lazy\ue000': 1})

Answer 3

我使用的最短路径是，

vocab_counter = Counter("the lazy fox jumps over the brown dog".split()) 
for key in vocab_counter.keys():
  vocab_counter[key+u"\uE000"] = vocab_counter.pop(key)

Answer 4

您可以通过字符串操作来完成：

text = 'the lazy fox jumps over the brown dog'
Counter((text + ' ').replace(' ', '_abc ').strip().split())

添加单个字符以在 Counter 中添加键

Adding a single character to add keys in Counter

python

string

counter

dictionary

key-value