如何将pandas数据帧中的稀疏矩阵转换为密集矩阵？

import pandas as pd
from scipy.sparse import csr_matrix

# 创建稀疏矩阵
data = [1, 2, 3]
row = [0, 1, 2]
col = [1, 2, 3]
sparse_matrix = csr_matrix((data, (row, col)), shape=(3, 4))

# 将稀疏矩阵转换为pandas数据帧
df = pd.DataFrame.sparse.from_spmatrix(sparse_matrix)

# 将稀疏矩阵转换为密集矩阵
dense_matrix = df.to_dense()

print(dense_matrix)

   0  1  2  3
0  0  1  0  0
1  0  0  2  0
2  0  0  0  3