简单 Pandas DataFrame read_csv 然后 GroupBy 与 Count / KeyError

Question

我只是想获取给定列中某个值的行数，例如：

CSV 数据：

'Occupation','data'
'Carpenter','data1'
'Carpenter','data2'
'Carpenter','data3'
'Painter','data1'
'Painter','data2'
'Programmer','data1'
'Programmer','data2'
'Programmer','data3'
'Programmer','data4'

程序:[=3​​0=]

filename = "./data/TestGroup.csv"

df = pd.read_csv(filename)
print(df.head())

print("Computing stats by HandRank... ")
df_stats = df[['data']].groupby(['Occupation']).agg(['count'])
# also tried:  df_stats = df[['Occupation']].groupby(['Occupation']).agg(['count'])
print(df_stats.head())

如何获取变量中的计数？ .groupby 和 .agg return 是另一个数据帧吗？

Output/Error:

  'Occupation'   'data'
0  'Carpenter'  'data1'
1  'Carpenter'  'data2'
2  'Carpenter'  'data3'
3    'Painter'  'data1'
4    'Painter'  'data2'
    Computing stats by HandRank... 
    Traceback (most recent call last):
      File "C:\Apps\PokerHandGenerator_Copy_not_Source\Server\TestPandasGroupBy.py", line 17, in <module>
        df_stats = df.groupby(['Occupation']).agg(['count'])
      File "C:\Apps\ProcessData\venv\lib\site-packages\pandas\core\frame.py", line 6714, in groupby
        return DataFrameGroupBy(
      File "C:\Apps\ProcessData\venv\lib\site-packages\pandas\core\groupby\groupby.py", line 560, in __init__
        grouper, exclusions, obj = get_grouper(
      File "C:\Apps\ProcessData\venv\lib\site-packages\pandas\core\groupby\grouper.py", line 811, in get_grouper
        raise KeyError(gpr)
    KeyError: 'Occupation'

df.head() 显示它使用“职业”作为我的列名称。

Answer 1

Pandas 将第一列视为 'Occupation' 而不是职业。

使用这个：-

df_stats = df.groupby("'Occupation'").agg(['count'])

而不是使用这个：-

df_stats = df[['data']].groupby(['Occupation']).agg(['count'])