python - 提取 numpy 3D 数组

Question

假设我有这个 pandas DataFrame:

>>> import pandas as pd, numpy as np
>>> df1 = pd.DataFrame([[np.nan, 2, np.nan, 0], [3, 4, np.nan, 1], [np.nan, np.nan, np.nan, 5]], columns=list('ABCD') )
>>> df = pd.concat([df1,df1], keys='EF', axis=1)
>>> df
     E                F
     A    B   C  D    A    B   C  D
0  NaN  2.0 NaN  0  NaN  2.0 NaN  0
1  3.0  4.0 NaN  1  3.0  4.0 NaN  1
2  NaN  NaN NaN  5  NaN  NaN NaN  5

如何将其转换为形状为 (3,2,4) 的 3D numpy 数组？

Answer 1

您可以 reshape values数据框:

import pandas as pd
import numpy as np

df1 = pd.DataFrame([[np.nan,      2, np.nan, 0],
                    [3,           4, np.nan, 1],
                    [np.nan, np.nan, np.nan, 5]],
                   columns=list('ABCD') )
df = pd.concat([df1, df1], keys='EF', axis=1)
# A view of the data, changing it changes df
df_three_dim = df.values.reshape((3, 2, 4))
# A new array, changing it does not change df
df_three_dim_copy = df.values.reshape((3, 2, 4)).copy()