fix and test bleu_hook.bleu_tokenize (#514)

* fix and test bleu_hook.bleu_tokenize

* make the test work in Python2

tensor2tensor/utils/bleu_hook.py

@@ -153,7 +153,7 @@ def __init__(self):
     def _property_chars(prefix):
       return ''.join(six.unichr(x) for x in range(sys.maxunicode)
                      if unicodedata.category(six.unichr(x)).startswith(prefix))
-    punctuation = self._property_chars('P')
+    punctuation = _property_chars('P')
     self.nondigit_punct_re = re.compile(r'([^\d])([' + punctuation + r'])')
     self.punct_nondigit_re = re.compile(r'([' + punctuation + r'])([^\d])')
     self.symbol_re = re.compile('([' + _property_chars('S') + '])')
@@ -183,9 +183,10 @@ def bleu_tokenize(string):
   Returns:
     a list of tokens
   """
-  string = UnicodeRegex.nondigit_punct_re.sub(r'\1 \2 ', string)
-  string = UnicodeRegex.punct_nondigit_re.sub(r' \1 \2', string)
-  string = UnicodeRegex.symbol_re.sub(r' \1 ', string)
+  uregex = UnicodeRegex()
+  string = uregex.nondigit_punct_re.sub(r'\1 \2 ', string)
+  string = uregex.punct_nondigit_re.sub(r' \1 \2', string)
+  string = uregex.symbol_re.sub(r' \1 ', string)
   return string.split()
 
 

tensor2tensor/utils/bleu_hook_test.py

@@ -57,5 +57,9 @@ def testComputeMultipleNgrams(self):
     actual_bleu = 0.3436
     self.assertAllClose(bleu, actual_bleu, atol=1e-03)
 
+  def testBleuTokenize(self):
+    self.assertEqual(bleu_hook.bleu_tokenize(u'hi, “there”'), [u'hi', u',', u'“', u'there', u'”'])
+
+
 if __name__ == '__main__':
   tf.test.main()