pandas.DataFrame->numpy.ndarray
import numpy as np
import pandas as pd
df = pd.DataFrame(data=[[1, 2, 3], [4, 5, 6]], columns=['a', 'b', 'c'])
print(df)
# a b c
# 0 1 2 3
# 1 4 5 6
a_df = df.values
print(a_df)
# [[1 2 3]
# [4 5 6]]
print(type(a_df))
# <class 'numpy.ndarray'>
print(a_df.dtype)
# int64
numpy.ndarray->pandas.DataFrame
a = np.arange(12).reshape((4, 3))
print(a)
# [[ 0 1 2]
# [ 3 4 5]
# [ 6 7 8]
# [ 9 10 11]]
df = pd.DataFrame(a)
print(df)
# 0 1 2
# 0 0 1 2
# 1 3 4 5
# 2 6 7 8
# 3 9 10 11