ValueError：使用序列设置数组元素

Question

i am trying to make an np.array from my dataframe column which contains float arrays of different lengths example of column:

[0.123123, 0.123123]
[1.123112]
[0.123123, 0.123123, 0.123123, 0.123123]

and i am getting ValueError: Setting an array element with sequence

i tried:

np.array(df['vector'].tolist())
np.array(df['vector'].squeeze())
np.array(df['vector'].tolist(), dtype=object)

and they all lead to ValueError

pandas version 0.23.4

Answer 1

If you want to concatenate all of nested elements in you data frame column to a single 1D array, you can use np.hstack .

import numpy as np
import pandas as pd

df = pd.DataFrame({'vector': [
    [0.123123, 0.123123],
    [1.123112],
    [0.123123, 0.123123, 0.123123, 0.123123]
    ]}
)

np.hstack(df['vector'])
# returns:
array([0.123123, 0.123123, 1.123112, 0.123123, 0.123123, 0.123123, 0.123123])