IndexError: index 8000 is out of bounds for axis 0 with size 8000

 一个新的数据集，处理后，代入之前跑了几次的代码，结果出现了问题，麻烦大家帮我指导一下。

# coding=utf-8
import pandas as pd
import numpy as np
import fasttext
from sklearn import metrics

with open('train_abstract.txt','w',encoding='utf-8') as f:
    for i in range(len(X_train.todense())):
        str1 = str(X_train.todense()[i])+"\t"+"__label__"+str(y_train.values[i])+'\n'
        f.write(str1)

with open('test_abstract.txt','w',encoding='utf-8') as f:
    for i in range(len(X_test)):
        str1 = str(X_test.values[i])+"\t"+"__label__"+str(y_test.values[i])+'\n'
        f.write(str1)


```python
IndexError                                Traceback (most recent call last)
<ipython-input-38-1b98cdb96387> in <module>()
      7 with open('train_abstract.txt','w',encoding='utf-8') as f:
      8     for i in range(len(X_train.todense())):
----> 9         str1 = str(X_train.todense()[i])+"\t"+"__label__"+str(y_train.values[i])+'\n'
     10         f.write(str1)
     11 

IndexError: index 8000 is out of bounds for axis 0 with size 8000

麻烦大家给我指导意见解决这个error， 非常感谢！