From 466f3c21ec7c07de98ae9979f2261e921260867a Mon Sep 17 00:00:00 2001
From: yunfan <yunfan.shao@outlook.com>
Date: Sat, 15 Sep 2018 19:53:48 +0800
Subject: [PATCH] add vocabulary

---
 fastNLP/data/vocabulary.py | 99 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 fastNLP/data/vocabulary.py

diff --git a/fastNLP/data/vocabulary.py b/fastNLP/data/vocabulary.py
new file mode 100644
index 00000000..3cff161b
--- /dev/null
+++ b/fastNLP/data/vocabulary.py
@@ -0,0 +1,99 @@
+from copy import deepcopy
+
+DEFAULT_PADDING_LABEL = '<pad>'  # dict index = 0
+DEFAULT_UNKNOWN_LABEL = '<unk>'  # dict index = 1
+DEFAULT_RESERVED_LABEL = ['<reserved-2>',
+                          '<reserved-3>',
+                          '<reserved-4>']  # dict index = 2~4
+
+DEFAULT_WORD_TO_INDEX = {DEFAULT_PADDING_LABEL: 0, DEFAULT_UNKNOWN_LABEL: 1,
+                         DEFAULT_RESERVED_LABEL[0]: 2, DEFAULT_RESERVED_LABEL[1]: 3,
+                         DEFAULT_RESERVED_LABEL[2]: 4}
+
+def isiterable(p_object):
+    try:
+        it = iter(p_object)
+    except TypeError: 
+        return False
+    return True
+
+class Vocabulary(object):
+    def __init__(self):
+        self.word2idx = deepcopy(DEFAULT_WORD_TO_INDEX)
+        self.padding_label = DEFAULT_PADDING_LABEL
+        self.unknown_label = DEFAULT_UNKNOWN_LABEL
+        self.idx2word = None
+
+    def __len__(self):
+        return len(self.word2idx)
+    
+    def update(self, word):
+        """add word or list of words into Vocabulary
+        """
+        if not isinstance(word, str) and isiterable(word):
+        # it's a nested list
+            for w in word:
+                self.update(w)
+        else:
+        # it's a word to be added
+            self.word2idx[word] = len(self)
+            if self.idx2word is not None:
+                self.idx2word = None
+
+    
+    def __getitem__(self, w):
+        """ like to_index(w) function, turn a word to the index
+            if w is not in Vocabulary, return the unknown label
+        """
+        if w in self.word2idx:
+            return self.word2idx[w]
+        else:
+            return self.word2idx[DEFAULT_UNKNOWN_LABEL]
+    
+    def unknown_idx(self):
+        return self.word2idx[self.unknown_label]
+    
+    def padding_idx(self):
+        return self.word2idx[self.padding_label]
+
+    def build_reverse_vocab(self):
+        self.idx2word = {self.word2idx[w] : w for w in self.word2idx}
+    
+    def to_word(self, idx):
+        """given a word's index, return the word itself
+        """
+        if self.idx2word is None:
+            self.build_reverse_vocab()
+        return self.idx2word[idx]
+    
+    def __getstate__(self):
+        """use to prepare data for pickle
+        """
+        state = self.__dict__.copy()
+        # no need to pickle idx2word as it can be constructed from word2idx
+        del state['idx2word']
+        return state
+    
+    def __setstate__(self, state):
+        """use to restore state from pickle
+        """
+        self.__dict__.update(state)
+        self.idx2word = None
+    
+if __name__ == '__main__':
+    import _pickle as pickle
+    vocab = Vocabulary()
+    filename = 'vocab'
+    vocab.update(filename)
+    vocab.update([filename, ['a'], [['b']], ['c']])
+    idx = vocab[filename]
+    print('{} {}'.format(vocab.to_word(idx), vocab[filename]))
+
+    with open(filename, 'wb') as f:
+        pickle.dump(vocab, f)
+    with open(filename, 'rb') as f:
+        vocab = pickle.load(f)
+    
+    print('{} {}'.format(vocab.to_word(idx), vocab[filename]))
+    print(vocab.word2idx)
+    
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