sklearn_crfsuite.CRF UnicodeEncodeError

Question

• python version: 3.6
• os: windows

I am trying to train a Chinese NER model with sklearn_crfsuite.CRF with ner_dataset. After I cleanup the dataset and fit the model, it shows the error message:

60loading training data to CRFsuite:   0%|                                                                                                                                                                     | 0/700 [00:00<?, ?it/s]
Traceback (most recent call last):
  File "main_script.py", line 22, in <module>
    crf_pipeline.model.fit(x_train, y_train, x_test, y_test)
  File "C:\Users\weber\PycharmProjects\demo-insurance-backend\venv\lib\site-packages\sklearn_crfsuite\estimator.py", line 314, in fit
    trainer.append(xseq, yseq)
  File "pycrfsuite\_pycrfsuite.pyx", line 312, in pycrfsuite._pycrfsuite.BaseTrainer.append
  File "stringsource", line 48, in vector.from_py.__pyx_convert_vector_from_py_std_3a__3a_string
  File "stringsource", line 15, in string.from_py.__pyx_convert_string_from_py_std__in_string
UnicodeEncodeError: 'ascii' codec can't encode characters in position 2-6: ordinal not in range(128)

The data format is in .txt seperated with \n, with OriginalText storing the text data and entities storing the entities information.
below is the code I preprocess the dataset:

import ast
from opencc import OpenCC
import sklearn_crfsuite

from sklearn.model_selection import train_test_split
from tqdm import tqdm

tag_dictionary = {
    '影像檢查': 'I-影像檢查',
    '手術': 'S-手術',
    '實驗室檢驗': 'E-實驗室檢驗',
    '解剖部位': 'B-解剖部位',
    '疾病和診斷': 'D-疾病和診斷'
}

def check_entity(entities):
    return [
        entity
        for entity in entities
        if entity['label_type'] in tag_dictionary
    ]

def build_tag_seq(text, entities):
    tag_list = ['O' for token in text]
    for entity in entities:
        if tag_dictionary is None:
            tag = entity['label_type']
        else:
            tag = tag_dictionary[entity['label_type']]
        tag_list[entity['start_pos']] = f'{tag}-B'
        for i in range(entity['start_pos']+1, entity['end_pos']):
            tag_list[i] = f'{tag}-I'
    return tag_list

def data_coverter(data):
    cc = OpenCC('s2t')  # 轉繁體
    data_dict = ast.literal_eval(cc.convert(data))  # txt轉dict
    return data_dict

def process_data(data):
    data_dict = data_coverter(data)
    text = data_dict['originalText']
    entities = data_dict['entities']
    entities = check_entity(entities)
    tag_seq = build_tag_seq(text, entities)
    return text, tag_seq

def load_txt_data(stop=-1):
    data_x = list()  # 內文(token序列)
    data_y = list()  # 每個token的對應tag序列
    for path in ['subtask1_training_part1.txt']:
        with open(path, 'r', encoding='utf-8') as f:
            for i, line in tqdm(enumerate(f.readlines())):
                text = line.strip()
                if len(text) > 3:
                    temp_x, temp_y = process_data(text)

                    data_x.append(temp_x)
                    data_y.append(temp_y)
                    if i == stop:
                        break
    return data_x, data_y

x, y = load_txt_data()

model = sklearn_crfsuite.CRF(
    algorithm='l2sgd',
    c2=1.0,
    max_iterations=1000,
    all_possible_transitions=True,
    all_possible_states=True,
    verbose=True
)

model.fit(x, y)

Below is pkgs list I used:

pip install opencc sklearn sklearn_crfsuite 

Does anyone get the similiar error message before and solved it? please, any help would be appreciated.

Answer 1

I figure out that I cannot use the Chinese symbols in NER tag from reference.
After changing the tag_dictionary with int in the value, it works.