如何在python中保存csv文件

import pandas as pd 
import numpy as np

data = pd.read_csv('C:\\abc\\a.csv', header=None)

col1 = data.values[:,0]
col2 = data.values[:,1]-0.9
for i in range(0, len(col2)):
    col2[i] = float("%.2f" % col2[i])
col3 = data.values[:,2]

data_arry = []
data_arry.append(col1)
data_arry.append(col2)
data_arry.append(col3)

np_data = np.array(data_arry)
np_data = np_data.T
np.array(np_data)
print(np_data)
save = pd.DataFrame(np_data, columns = ['year', 'month', 'day']) 
save.to_csv('C:\\abc\\a_modified.csv',index=False,header=False)  #index=False,header=False表示不保存行索引和列标题