Question

my test.csv

1,1,2
2,1,3
3,1,4

my test2.csv

2,3
2,3
2,3

如何制作output.csv：

1,1,2,2,3
2,1,3,2,3
3,1,4,2,3

所以将两个csv文件合并为一个？

这是我的代码

import csv, os, sys
with open('test.csv', 'rb') as input, open('output.csv', 'wb') as output, open ('test2.csv', 'rb') as input2:
        reader = csv.reader(input, delimiter = ',')
        reader2 = csv.reader(input2, delimiter = ',')
        writer = csv.writer(output, delimiter = ',')

        all = []                                        
        header = next(reader)
        all.append(header)
        count = 0
        for row,row2 in reader and reader2:
                count += 1
                while count:
                        all.append(row+row2)
                        break
        writer.writerows(all)

显然这不起作用，但有人知道我的目的是什么吗？

Answer 1

使用zip()一次迭代两个读者：

reader1 = csv.reader(input, delimiter = ',')
reader2 = csv.reader(input2, delimiter = ',')

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

或更短的版本：

writer.writerows(map(list.__add__, row1, row2))

如果文件很大，那么使用map，zip在Python 2中不是一个好主意，因为它们将加载两个文件中的所有行，最好是它们的迭代器存在的版本 itertools模块：itertools.imap和itertools.izip：

for row,row2 in reader and reader2:相当于只迭代reader2，因为and works是这样的：

>>> 1 and 2 
2
>>> 2 and 3
3
>>> 0 and 2  # returned the first falsy value, but as an iterator is not a falsy value
0            # so it will return `reader2` in your case.

<强>更新

要就地更新test2.csv，您可以使用fileinput模块，但是这样您就无法使用csv模块。

>>> import fileinput
>>> with open('test.csv') as f:
    for line in fileinput.input('test2.csv', inplace=True):
        print next(f).rstrip() + ',' + line,
...         
>>> !cat test2.csv
1,1,2,2,3
2,1,3,2,3
3,1,4,2,3

使用csv模块，您必须首先从内存中的test2.csv读取所有行，然后将新数据写入其中。

with open('test.csv') as f1, open('test2.csv', 'r+') as f2:
                                   #open in r+ mode
   reader1 = csv.reader(f1)
   rows_f2 = list(csv.reader(f2)) #read all the rows
   f2.truncate(0)                 #truncate the file
   writer = csv.writer(f2)
   writer.writerows(map(list.__add__, reader1, rows_f2))

Answer 2

只需用逗号串行连接......

with open('test.csv', 'rb') as input, open('output.csv', 'wb') as output, open ('test2.csv', 'rb') as input2:
    for row, row2 in zip(input, input2):
        output.write(row.rstrip('\n') + ',' + row2)

如何将2个不同文件中的列添加到CSV python中的输出

2 个答案: