在Python中使用nltk模块拆分单词

Question

我正在尝试找到一种使用nltk模块在Python中拆分单词的方法。考虑到我拥有的原始数据（例如带符号词的列表），我不确定如何达到我的目标

['usingvariousmolecularbiology', 'techniques', 'toproduce', 'genotypes', 'following', 'standardoperatingprocedures', '.', 'Operateandmaintainautomatedequipment', '.', 'Updatesampletrackingsystemsandprocess', 'documentation', 'toallowaccurate', 'monitoring', 'andrapid', 'progression', 'ofcasework']

如您所见，许多单词被粘在一起（即“ to”和“ produce”被粘在一个字符串“ toproduce”中）。这是从PDF文件中抓取数据的一种人工产物，我想找到一种使用python中的nltk模块将卡住的单词拆分（即，将“ toproduce”拆分为两个单词：“ to”和“ produce”的方法）；将“ standardoperatingprocedures”分为三个词：“ standard”，“ operating”，“ procedures”）。

感谢您的帮助！

Answer 1

我相信您会在这种情况下使用分词，而且我不知道NLTK中的任何分词功能都可以处理没有空格的英语句子。您可以pyenchant改用。我仅以示例方式提供以下代码。（它适用于少量的相对较短的字符串（例如示例列表中的字符串），但对于较长的字符串或更多的字符串而言效率很低。）它将需要进行修改，并且不会成功地对每个字符串进行分段在任何情况下都为字符串。

import enchant  # pip install pyenchant
eng_dict = enchant.Dict("en_US")

def segment_str(chars, exclude=None):
    """
    Segment a string of chars using the pyenchant vocabulary.
    Keeps longest possible words that account for all characters,
    and returns list of segmented words.

    :param chars: (str) The character string to segment.
    :param exclude: (set) A set of string to exclude from consideration.
                    (These have been found previously to lead to dead ends.)
                    If an excluded word occurs later in the string, this
                    function will fail.
    """
    words = []

    if not chars.isalpha():  # don't check punctuation etc.; needs more work
        return [chars]

    if not exclude:
        exclude = set()

    working_chars = chars
    while working_chars:
        # iterate through segments of the chars starting with the longest segment possible
        for i in range(len(working_chars), 1, -1):
            segment = working_chars[:i]
            if eng_dict.check(segment) and segment not in exclude:
                words.append(segment)
                working_chars = working_chars[i:]
                break
        else:  # no matching segments were found
            if words:
                exclude.add(words[-1])
                return segment_str(chars, exclude=exclude)
            # let the user know a word was missing from the dictionary,
            # but keep the word
            print('"{chars}" not in dictionary (so just keeping as one segment)!'
                  .format(chars=chars))
            return [chars]
    # return a list of words based on the segmentation
    return words

如您所见，此方法（大概）仅对字符串之一进行了错误分段：

>>> t = ['usingvariousmolecularbiology', 'techniques', 'toproduce', 'genotypes', 'following', 'standardoperatingprocedures', '.', 'Operateandmaintainautomatedequipment', '.', 'Updatesampletrackingsystemsandprocess', 'documentation', 'toallowaccurate', 'monitoring', 'andrapid', 'progression', 'ofcasework']
>>> [segment(chars) for chars in t]
"genotypes" not in dictionary (so just keeping as one segment)
[['using', 'various', 'molecular', 'biology'], ['techniques'], ['to', 'produce'], ['genotypes'], ['following'], ['standard', 'operating', 'procedures'], ['.'], ['Operate', 'and', 'maintain', 'automated', 'equipment'], ['.'], ['Updates', 'ample', 'tracking', 'systems', 'and', 'process'], ['documentation'], ['to', 'allow', 'accurate'], ['monitoring'], ['and', 'rapid'], ['progression'], ['of', 'casework']]

然后，您可以chain用来展平此列表列表：

>>> from itertools import chain
>>> list(chain.from_iterable(segment_str(chars) for chars in t))
"genotypes" not in dictionary (so just keeping as one segment)!
['using', 'various', 'molecular', 'biology', 'techniques', 'to', 'produce', 'genotypes', 'following', 'standard', 'operating', 'procedures', '.', 'Operate', 'and', 'maintain', 'automated', 'equipment', '.', 'Updates', 'ample', 'tracking', 'systems', 'and', 'process', 'documentation', 'to', 'allow', 'accurate', 'monitoring', 'and', 'rapid', 'progression', 'of', 'casework']