將另一列添加到CSV文件w/python

Question

我正在尋找添加另一列到CSV文件w/python。

file1的是日期.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的被Price.csv

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

我的期望的輸出是（在日期.csv）

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 

但我回來的是重複

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

我的程序的價格如下

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) 

欣賞一些指導，歡呼聲

Answer 1

您不能只將一列寫入現有文件。最好的選擇是創建一個新文件。如果數據是爲了讓這兩個文件，那麼你可以簡單地壓縮起來，並寫出更新的字典出：

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) 

大熊貓也有另一種選擇：

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') 

輸出：

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

需要3個文件在同一時間，和從第二個文件

追加只需要列

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]]) 

而輸出：

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