KeyError：0熊猫

Question

我需要帮助。我试图过滤掉并写入另一个csv文件，该文件由elapsed_seconds列中的10769s之后收集的数据以及加速度大小组成。但是，我得到KeyError异常：0 ...那我收到

import numpy as np 
import pandas as pd 
import matplotlib.pyplot as plt 

data = pd.read_csv(accelDataPath) 
data.columns = ['t', 'x', 'y', 'z'] 

# calculate the magnitude of acceleration 
data['m'] = np.sqrt(data['x']**2 + data['y']**2 + data['z']**2) 

data['datetime'] = pd.DatetimeIndex(pd.to_datetime(data['t'], unit = 'ms').dt.tz_localize('UTC').dt.tz_convert('US/Eastern')) 
data['elapsed_seconds'] = (data['datetime'] - data['datetime'].iloc[0]).dt.total_seconds() 
i=0 
csv = open("filteredData.csv", "w+") 
csv.write("Event at, Magnitude \n") 
while (i < len(data[data.elapsed_seconds > 10769])): 
    csv.write(str(data[data.elapsed_seconds > 10769][i]) + ", " + str(data[data.m][i]) + "\n") 
csv.close() 

错误是：

Traceback (most recent call last): 
    File "C:\Users\Desktop\AnalyzingData.py", line 37, in <module> 
csv.write(str(data[data.elapsed_seconds > 10769][i]) + ", " + str(data[data.m][i]) + "\n") 
    File "C:\python\lib\site-packages\pandas\core\frame.py", line 1964, in __getitem__ 
    return self._getitem_column(key) 
    File "C:\python\lib\site-packages\pandas\core\frame.py", line 1971, in _getitem_column 
    return self._get_item_cache(key) 
    File "C:\python\lib\site-packages\pandas\core\generic.py", line 1645, in _get_item_cache 
    values = self._data.get(item) 
    File "C:\python\lib\site-packages\pandas\core\internals.py", line 3590, in get 
    loc = self.items.get_loc(item) 
    File "C:\python\lib\site-packages\pandas\core\indexes\base.py", line 2444, in get_loc 
    return self._engine.get_loc(self._maybe_cast_indexer(key)) 
    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: 0 

Answer 1

改变这一行

csv.write(
    str(data[data.elapsed_seconds > 10769][i]) + ", " + str(data[data.m][i]) + "\n" 
    ) 

要这样：

csv.write(
    str(data[data.elapsed_seconds > 10769].iloc[i]) + ", " + str(data[data.m].iloc[i]) +"\n" 
    ) 

另外，请注意，您没有增加i，就像这个i += 1一样，在while循环中。

---

或者，更好，使用df.to_csv如下：

import numpy as np 
import pandas as pd 
import matplotlib.pyplot as plt 

data = pd.read_csv(accelDataPath) 
data.columns = ['t', 'x', 'y', 'z'] 

# calculate the magnitude of acceleration 
data['m'] = np.sqrt(data['x']**2 + data['y']**2 + data['z']**2) 

data['datetime'] = pd.DatetimeIndex(pd.to_datetime(data['t'], unit = 'ms').dt.tz_localize('UTC').dt.tz_convert('US/Eastern')) 
data['elapsed_seconds'] = (data['datetime'] - data['datetime'].iloc[0]).dt.total_seconds() 

# write to csv using data.to_csv 
data[data.elapsed_seconds > 10769][['elapsed_seconds', 'm']].to_csv("filteredData.csv", 
      sep=",", 
      index=False)