IndexError：列表索引超出打开pickle文件的范围

Question

我在解析我在另一个程序中腌制的数据文件时遇到'IndexError: list index out of range'错误。我使用的是Python 3.5.2和Tensorflow v1.0。以下是代码。

酸洗代码：

if __name__ == '__main__':
train_x, train_y, test_x, test_y = create_feature_sets_and_labels('pos.txt', 'neg.txt')
with open('sentiment_set.pickle', 'wb') as f:
    pickle.dump([train_x, train_y, test_x, test_y], f)

非腌制代码：

import tensorflow as tf
import numpy as np
import pickle
with open("sentiment_set.pickle", "rb") as f:
    train_x, train_y, test_x, test_y = pickle.load(f)
size = len(train_x[0])
print(size)

输出是：

Traceback (most recent call last):
File "4_sentiment_neural_network.py", line 11, in <module>
size = len(train_x[0])
IndexError: list index out of range

即使我尝试打印出train_x [0]，使用下面的代码，我仍然会得到完全相同的错误。

size = list(train_x[0])
print(size)

我不明白这一点，错误是什么以及如何纠正错误？