参考：https://numpy.org/doc/stable/reference/generated/numpy.ndarray.flatten.html

语法格式

ndarray.flatten(order='C')

order: “C”表示按行(C-style)顺序折叠。“F”表示按列(Fortran-style)顺序进行平化。' A '表示：如果A在内存中是Fortran连续的，则按列顺序平化，否则按行顺序平化。“K”表示按元素在内存中出现的顺序平坦化。默认为' C '。

返回：一个输入数组的一个拷贝，平展为一维的ndarray。

代码示例

import pandas as pd
import numpy as np
#利用列表创建DataFrame
data = [[0,"negative",2],[1,"negative",6],[2,"positive",0],[3,"positive",2]]
b = np.array(data)
print(b)
# output
# [['0' 'negative' '2']
#  ['1' 'negative' '6']
#  ['2' 'positive' '0']
#  ['3' 'positive' '2']]
print(b.flatten())
# output 
# ['0' 'negative' '2' '1' 'negative' '6' '2' 'positive' '0' '3' 'positive' '2']