路径优化模型中使用pandas库访问索引的时候出现错误，请帮助！

There's nothing shown about what values of your dataframe and key/index, how people can help ?

A short program that isolates and demonstrates the problem (Do not paste your massive program, but instead 10-20 lines that executable and clearly show the problem)

For example, find all the values of related variables by print statement before exception happed when which statement called. So you can reduce your code to

import pandas as pd

# What values before exception happened
data = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
df = pd.DataFrame(data, columns=['A','b','c'])

# exception happened when index by key 1
key = 1
print(df[key])

Exception information

Traceback (most recent call last):
  File "C:\Software\Python\lib\site-packages\pandas\core\indexes\base.py", line 3805, in get_loc
    return self._engine.get_loc(casted_key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "index.pyx", line 167, in pandas._libs.index.IndexEngine.get_loc
  File "index.pyx", line 196, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\\_libs\\hashtable_class_helper.pxi", line 7081, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas\\_libs\\hashtable_class_helper.pxi", line 7089, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 1

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "D:\test.py", line 9, in <module>
    print(df[key])
          ~~^^^^^
  File "C:\Software\Python\lib\site-packages\pandas\core\frame.py", line 4102, in __getitem__
    indexer = self.columns.get_loc(key)
              ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Software\Python\lib\site-packages\pandas\core\indexes\base.py", line 3812, in get_loc
    raise KeyError(key) from err
KeyError: 1

Then we can find the answer is that there's no key 1 for dataframe df.

把你的dataframe多少打印出来一些，或者你的代码提供一下，这个错误很可能是loc[i, t] 的第二个参数t引起的，但是也不是很确定。