求组，求助，求助，python pandas error！！！困扰致死

一个雷电

listings=pd.read_excel('listings.xlsx')#这是一个有三个sheet的excel表格，这个表格的三个sheet名称就是exchanges里的那三个
# Create the list exchanges
exchanges = [ 'amex','nasdaq', 'nyse']
# Iterate over exchanges then plot and show result
for exchange in exchanges:
    sectors = listings[exchange].Sector.value_counts()
    #.value_counts():count of each unique value
    # Sort in descending order and plot
    sectors.sort_values(ascending=False).plot(kind='bar')
    # Show the plot
    plt.show()


结果出现这样的错误：
Traceback (most recent call last):
  File "/Users/apple/Library/Python/3.7/lib/python/site-packages/pandas/core/indexes/base.py", line 2657, in get_loc
    return self._engine.get_loc(key)
  File "pandas/_libs/index.pyx", line 108, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/index.pyx", line 132, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/hashtable_class_helper.pxi", line 1601, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas/_libs/hashtable_class_helper.pxi", line 1608, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 'amex'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/apple/Desktop/python_work/data camp/import and manage financila data/import and manage financial data 2.py", line 18, in <module>
    sectors = listings[exchange].Sector.value_counts()
  File "/Users/apple/Library/Python/3.7/lib/python/site-packages/pandas/core/frame.py", line 2927, in __getitem__
    indexer = self.columns.get_loc(key)
  File "/Users/apple/Library/Python/3.7/lib/python/site-packages/pandas/core/indexes/base.py", line 2659, in get_loc
    return self._engine.get_loc(self._maybe_cast_indexer(key))
  File "pandas/_libs/index.pyx", line 108, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/index.pyx", line 132, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/hashtable_class_helper.pxi", line 1601, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas/_libs/hashtable_class_helper.pxi", line 1608, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 'amex'
[Finished in 2.7s with exit code 1]
求解求解，我怀疑是导入文件dataframe的问题，因为除了第一个导入excel文件的语句，下面的语句在Datacamp的教学ipython shell里是正常运行的。

casanava

代码开始导入
import pandas as pd

一个雷电

casanava 发表于 2019-4-4 07:33
代码开始导入
import pandas as pd

这些模块我都导入啦

import pandas as pd
import numpy as np
import seaborn as sns
from datetime import date
from pandas_datareader.data import DataReader
import matplotlib.pyplot as plt

塔利班

这里使用了read_excel()方法来读取excel，来看一个read_excel()这个方法的API，这里只截选一部分经常使用的参数：

pd.read_excel(io, sheet_name=0, header=0, names=None, index_col=None, usecols=None)
1
这里主要参数为io，sheet_name，header，usecols和names

io：excel文件，如果命名为中文，在python2.7中，需要使用decode()来解码成unicode字符串，例如： pd.read_excel('示例'.decode('utf-8))

sheet_name：返回指定的sheet，如果将sheet_name指定为None，则返回全表，如果需要返回多个表，可以将sheet_name指定为一个列表，例如['sheet1', 'sheet2']