code: import re
  from typing import List
  
  import numpy as np
  
  # pylint: disable=too-few-public-methods
  
  ID_SEP = re.compile(r"[-:]")
  
  
  class WordAlignmentPreprocessor(object):
      """A preprocessor for word alignments in a text format.
  
      One of the following formats is expected:
  
          s1-t1 s2-t2 ...
  
          s1:1/w1 s2:t2/w2 ...
  
      where each `s` and `t` is the index of a word in the source and target
      sentence, respectively, and `w` is the corresponding weight. If the weight
      is not given, it is assumend to be 1. The separators `-` and `:` are
      interchangeable.
  
      The output of the preprocessor is an alignment matrix of the fixed shape
      (target_len, source_len) for each sentence.
      """
  
      def __init__(self, source_len, target_len, dtype=np.float32,
                   normalize=True, zero_based=True):
          self._source_len = source_len
          self._target_len = target_len
          self._dtype = dtype
          self._normalize = normalize
          self._zero_based = zero_based
  
      def __call__(self, sentence: List[str]):
          result = np.zeros((self._target_len, self._source_len), self._dtype)
  
          for ali in sentence:
              ids, _, str_weight = ali.partition("/")
              i, j = [int(id_str) for id_str in ID_SEP.split(ids)]
              weight = float(str_weight) if str_weight else 1.
  
              if not self._zero_based:
                  i -= 1
                  j -= 1
  
              if i < self._source_len and j < self._target_len:
                  result[j][i] = weight
  
          if self._normalize:
              with np.errstate(divide="ignore", invalid="ignore"):
                  result /= result.sum(axis=1, keepdims=True)
                  result[np.isnan(result)] = 0
  
          return result
  
apis: numpy.isnan numpy.zeros numpy.errstate