Improve metaclass handling

Also, no longer need u() and b()

Author: sloria

text/base.py

@@ -7,12 +7,11 @@
 from __future__ import absolute_import
 from abc import ABCMeta, abstractmethod
 from text.packages import nltk
-from text.compat import add_metaclass
+from text.compat import with_metaclass
 
 ##### POS TAGGERS #####
 
-@add_metaclass(ABCMeta)
-class BaseTagger(object):
+class BaseTagger(with_metaclass(ABCMeta)):
 
     '''Abstract tagger class from which all taggers
     inherit from. All descendants must implement a
@@ -27,8 +26,7 @@ def tag(self, text, tokenize=True):
 
 ##### NOUN PHRASE EXTRACTORS #####
 
-@add_metaclass(ABCMeta)
-class BaseNPExtractor(object):
+class BaseNPExtractor(with_metaclass(ABCMeta)):
 
     '''Abstract base class from which all NPExtractor classes inherit.
     Descendant classes must implement an ``extract(text)`` method
@@ -42,8 +40,7 @@ def extract(self, text):
 
 ##### TOKENIZERS #####
 
-@add_metaclass(ABCMeta)
-class BaseTokenizer(nltk.tokenize.api.TokenizerI):
+class BaseTokenizer(with_metaclass(ABCMeta), nltk.tokenize.api.TokenizerI):
 
     '''Abstract base class from which all Tokenizer classes inherit.
     Descendant classes must implement a ``tokenize(text)`` method
@@ -71,8 +68,8 @@ def itokenize(self, text, *args, **kwargs):
 DISCRETE = 'ds'
 CONTINUOUS = 'co'
 
-@add_metaclass(ABCMeta)
-class BaseSentimentAnalyzer(object):
+
+class BaseSentimentAnalyzer(with_metaclass(ABCMeta)):
 
     '''Abstract base class from which all sentiment analyzers inherit.
     Should implement an ``analyze(text)`` method which returns either the
@@ -99,8 +96,7 @@ def analyze(self, text):
 
 ##### PARSERS #####
 
-@add_metaclass(ABCMeta)
-class BaseParser(object):
+class BaseParser(with_metaclass(ABCMeta)):
 
     '''Abstract parser class from which all parsers inherit from. All
     descendants must implement a `parse()` method.

text/classifiers.py

@@ -34,7 +34,7 @@
 from __future__ import absolute_import
 from text.packages import nltk
 from text.tokenizers import WordTokenizer
-from text.compat import basestring, u
+from text.compat import basestring
 import text.formats as formats
 from text.utils import lowerstrip
 from text.decorators import cached_property
@@ -74,7 +74,7 @@ def basic_extractor(document, train_set):
                     for w in tokenizer.itokenize(document, include_punc=False)])
     else:
         tokens = set((lowerstrip(w, all=False) for w in document))
-    features = dict([(u('contains({0})').format(word), (word in tokens))
+    features = dict([(u'contains({0})'.format(word), (word in tokens))
                                             for word in word_features])
     return features
 
@@ -89,7 +89,7 @@ def contains_extractor(document):
                     for w in tokenizer.itokenize(document, include_punc=False)])
     else:
         tokens = set((lowerstrip(w, all=False) for w in document))
-    features = dict((u('contains({0})'.format(w)), True) for w in tokens)
+    features = dict((u'contains({0})'.format(w), True) for w in tokens)
     return features
 
 ##### CLASSIFIERS #####

text/compat.py

@@ -4,10 +4,6 @@
 PY2 = int(sys.version[0]) == 2
 
 if PY2:
-    def b(s):
-        return s
-    def u(s):
-        return unicode(s, "unicode_escape")
     from itertools import imap, izip
     import urllib2 as request
     from urllib import quote as urlquote
@@ -27,12 +23,7 @@ def implements_to_string(cls):
         cls.__unicode__ = cls.__str__
         cls.__str__ = lambda x: x.__unicode__().encode('utf-8')
         return cls
-
 else: # PY3
-    def b(s):
-        return s.encode("latin-1")
-    def u(s):
-        return s
     from urllib import request
     from urllib.parse import quote as urlquote
     text_type = str
@@ -47,15 +38,21 @@ def u(s):
     implements_to_string = lambda x: x
 
 
-def add_metaclass(metaclass):
-    """Class decorator for creating a class with a metaclass.
-    From the six library.
-    """
-    def wrapper(cls):
-        orig_vars = cls.__dict__.copy()
-        orig_vars.pop('__dict__', None)
-        orig_vars.pop('__weakref__', None)
-        for slots_var in orig_vars.get('__slots__', ()):
-            orig_vars.pop(slots_var)
-        return metaclass(cls.__name__, cls.__bases__, orig_vars)
-    return wrapper
+def with_metaclass(meta, *bases):
+    '''Defines a metaclass.
+
+    Creates a dummy class with a dummy metaclass. When subclassed, the dummy
+    metaclass is used, which has a constructor that instantiates a
+    new class from the original parent. This ensures that the dummy class and
+    dummy metaclass are not in the inheritance tree.
+
+    Credit to Armin Ronacher.
+    '''
+    class metaclass(meta):
+        __call__ = type.__call__
+        __init__ = type.__init__
+        def __new__(cls, name, this_bases, d):
+            if this_bases is None:
+                return type.__new__(cls, name, (), d)
+            return meta(name, bases, d)
+    return metaclass('temporary_class', None, {})