python怎样保存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