Pandas error: "pandas.libs.hashtable.PyObjectHashTable.get_item (pandas / _ libs / hashtable.c: 20477)

First of all, hello everyone. I'm halfway there though Python Programming for Finance is creating targets for machine learning labels , and I have a csv with some historical stock data I'm reading into pandas:

def process_data_for_labels(ticker):
    hm_days = 7
    df = pd.read_csv('file.csv', index_col=0)
    tickers = df.columns.values.tolist()
    df.fillna(0, inplace=True)

for i in range(1, hm_days + 1):
    df['{}_{}d'.format(ticker, i)] = (df[ticker].shift(-i) - df[ticker]) / df[ticker]

df.fillna(0, inplace=True)
return tickers, df

def buy_sell_hold(*args):
    cols = [c for c in args]
    requirement = 0.02
    for col in cols:
        if col > requirement:
            # Buy = 1 , Sell = 1 , Hold = 0
            return 1
        if col < -requirement:
            return -1
    return 0


def extract_featuresets(ticker):
    tickers, df = process_data_for_labels(ticker)

    df['{}_target'.format(ticker)] = list(map(buy_sell_hold,
                                          df['{}_1d'.format(ticker)],
                                          df['{}_2d'.format(ticker)],
                                          df['{}_3d'.format(ticker)],
                                          df['{}_4d'.format(ticker)],
                                          df['{}_5d'.format(ticker)],
                                          df['{}_6d'.format(ticker)],
                                          df['{}_7d'.format(ticker)]
                                          ))

vals = df['{}_target'.format(ticker)].values.tolist()
str_vals = [str(i) for i in vals]
print('Data spread:', Counter(str_vals))

df.fillna(0, inplace=True)
df = df.replace([np.inf, -np.inf], np.nan)
df.dropna(inplace=True)

df_vals = df[[ticker for ticker in tickers]].pct_change()
df_vals = df_vals.replace([np.inf, -np.inf], 0)
df_vals.fillna(0, inplace=True)

X = df_vals.values
y = df['{}_target'.format(ticker)].values

return X, y, df

extract_featuresets('XOM')

      

        
        
        
      

    

However, when I run it, I get the following error:

File "pandas\_libs\index.pyx", line 132, in pandas._libs.index.IndexEngine.get_loc (pandas\_libs\index.c:5280)
  File "pandas\_libs\index.pyx", line 154, in pandas._libs.index.IndexEngine.get_loc (pandas\_libs\index.c:5126)
  File "pandas\_libs\hashtable_class_helper.pxi", line 1210, in pandas._libs.hashtable.PyObjectHashTable.get_item (pandas\_libs\hashtable.c:20523)
  File "pandas\_libs\hashtable_class_helper.pxi", line 1218, in pandas._libs.hashtable.PyObjectHashTable.get_item (pandas\_libs\hashtable.c:20477)
KeyError: 'ZTS_target'

      

        
        
        
      

    

By the appearance of the error, I think it was complaining about the ZTS column data, tried formatting it differently, and when all else failed, I tried to remove it, and then the error hit the company column data right in front of it.

If you run the function with extract_featuresets('ZTS')

, it won't work, but with all other tickers.

Any ideas how to fix this? Thank!