使用python将另一列添加到CSV文件

Question

我想将另一列添加到带python的CSV文件中。

file1是Date.csv具有格式

ID, Date
0,"Jan 22, 2016"
1,"Jan 21, 2016"
2,"Jan 20, 2016"
3,"Jan 19, 2016"

和

file2是Price.csv

ID, Price
0,27.89
1,26.80
2,26.78
3,26.00

我想要的输出是（在Date.csv中）

ID, Date
0,"Jan 22, 2016", 27.89
1, "Jan 21, 2016", 26.80
2, "Jan 20, 2016", 26.78
3, "Jan 19, 2016", 26.00

但是我要返回的是重复的价格

0,27.89,27.89
1,26.80,26.80
2,26.78,26.78
3,26.00,26.00

我的程序如下

import csv

with open('C:/Users/User/OneDrive/Documents/Price.csv','r') as csvinput:
    with open('C:/Users/User/OneDrive/Documents/Date.csv', 'w') as csvoutput:
        writer = csv.writer(csvoutput, lineterminator='\n')
        reader = csv.reader(csvinput)

        all = []
        row = next(reader)

        for row in reader:
            row.append(row[1])
            all.append(row)

        writer.writerows(all)

赞赏一些指导，欢呼

Answer 1

您同时需要3个文件，并仅从第二个文件追加所需的列

import csv

date_reader = csv.reader(open('Date.csv', 'rb'))
price_reader = csv.reader(open('Price.csv', 'rb'))
writer = csv.writer(open('NewData.csv', 'wb'))
for date_row in date_reader:
    price_row = price_reader.next()
    writer.writerow(date_row + [price_row[1]])

并输出：

ID, Date, Price
0,"Jan 22, 2016",27.89
1,"Jan 21, 2016",26.80
2,"Jan 20, 2016",26.78
3,"Jan 19, 2016",26.00

Answer 2

您不能只将一列写入现有文件。 最好的选择是创建一个新文件。 如果数据符合两个文件的顺序，则只需将它们压缩并写出更新的字典即​​可：

with open('C:/Users/User/OneDrive/Documents/Date.csv') as file1, \
     open('C:/Users/User/OneDrive/Documents/Price.csv') as file2, \
     open('C:/Users/User/OneDrive/Documents/Output.csv', 'w') as output:
    reader1 = csv.DictReader(file1)
    reader2 = csv.DictReader(file2)
    writer = csv.DictWriter(output, ['ID', 'Date', 'Price'])
    writer.writeheader()  # Optional if you want the header

    for row1, row2 in zip(reader1, reader2):
        row1.update(row2)
        writer.writerow(row1)

熊猫也是另一个选择：

import pandas as pd
file1 = pd.read_csv('Data.csv', index_col='ID')
file2 = pd.read_csv('Price.csv', index_col='ID')
pd.concat([file1,file2], axis=1).to_csv('Output.csv')

输出：

ID,Date,Price
0,"Jan 22, 2016",27.89
1,"Jan 21, 2016",26.80
2,"Jan 20, 2016",26.78
3,"Jan 19, 2016",26.00