Better alphabet access

bin/import_swc.py

@@ -159,13 +159,7 @@ def read_token(token):
 
 
 def in_alphabet(alphabet, c):
-    if alphabet is None:
-        return False
-    try:
-        alphabet.label_from_string(c)
-        return True
-    except KeyError:
-        return False
+    return True if alphabet is None else alphabet.has_char(c)
 
 
 alphabets = {}
@@ -200,7 +194,7 @@ def label_filter(label, language):
                             .encode("ascii", "ignore")
                             .decode("ascii", "ignore"))
         for sc in c:
-            if alphabet is not None and not in_alphabet(alphabet, sc):
+            if not in_alphabet(alphabet, sc):
                 return None, 'illegal character'
             chars.append(sc)
     label = ''.join(chars)

util/text.py

@@ -36,6 +36,9 @@ class Alphabet(object):
                 'then add all these to data/alphabet.txt.'.format(string)
             ).with_traceback(e.__traceback__)
 
+    def has_char(self, char):
+        return char in self._str_to_label
+
     def encode(self, string):
         res = []
         for char in string: