# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from collections import OrderedDict
from typing import Iterable
__all__ = ["Vocab"]
[docs]class Vocab(object):
""" Vocabulary.
Args:
symbols (Iterable[str]): Common symbols.
padding_symbol (str, optional): Symbol for pad. Defaults to "<pad>".
unk_symbol (str, optional): Symbol for unknow. Defaults to "<unk>"
start_symbol (str, optional): Symbol for start. Defaults to "<s>"
end_symbol (str, optional): Symbol for end. Defaults to "</s>"
"""
def __init__(self,
symbols: Iterable[str],
padding_symbol="<pad>",
unk_symbol="<unk>",
start_symbol="<s>",
end_symbol="</s>"):
self.special_symbols = OrderedDict()
for i, item in enumerate(
[padding_symbol, unk_symbol, start_symbol, end_symbol]):
if item:
self.special_symbols[item] = len(self.special_symbols)
self.padding_symbol = padding_symbol
self.unk_symbol = unk_symbol
self.start_symbol = start_symbol
self.end_symbol = end_symbol
self.stoi = OrderedDict()
self.stoi.update(self.special_symbols)
for i, s in enumerate(symbols):
if s not in self.stoi:
self.stoi[s] = len(self.stoi)
self.itos = {v: k for k, v in self.stoi.items()}
def __len__(self):
return len(self.stoi)
@property
def num_specials(self):
""" The number of special symbols.
"""
return len(self.special_symbols)
# special tokens
@property
def padding_index(self):
""" The index of padding symbol
"""
return self.stoi.get(self.padding_symbol, -1)
@property
def unk_index(self):
"""The index of unknow symbol.
"""
return self.stoi.get(self.unk_symbol, -1)
@property
def start_index(self):
"""The index of start symbol.
"""
return self.stoi.get(self.start_symbol, -1)
@property
def end_index(self):
""" The index of end symbol.
"""
return self.stoi.get(self.end_symbol, -1)
def __repr__(self):
fmt = "Vocab(size: {},\nstoi:\n{})"
return fmt.format(len(self), self.stoi)
def __str__(self):
return self.__repr__()
[docs] def lookup(self, symbol):
""" The index that symbol correspond.
"""
return self.stoi[symbol]
[docs] def reverse(self, index):
""" The symbol thar index cottespond.
"""
return self.itos[index]
[docs] def add_symbol(self, symbol):
""" Add a new symbol in vocab.
"""
if symbol in self.stoi:
return
N = len(self.stoi)
self.stoi[symbol] = N
self.itos[N] = symbol
[docs] def add_symbols(self, symbols):
""" Add multiple symbols in vocab.
"""
for symbol in symbols:
self.add_symbol(symbol)