在CSV列中插入整数列表于其他数据后

Question

我想在一个CSV文件中插入一个新列，放在已有数据的后面。比如，我的CSV文件现在包含：

   Heading 1     Heading 2
   1 
   1
   0
   2
   1
   0

我有一个整数列表，格式是：

 [1,0,1,2,1,2,1,1]

我该如何把这个列表插入到CSV文件的“Header 2”下面呢？

到目前为止，我只能做到把新的整数列表加在现有数据的下面，比如：

   Heading 1     Heading 2
   1 
   1
   0
   2
   1
   0
   1
   0
   1
   2
   1
   2
   1
   1

使用的代码是：

 #Open CSV file
 with open('C:\Data.csv','wb') as g:
            #New writer
    gw = csv.writer(g)
            #Add headings
    gw.writerow(["Heading 1","Heading 2"])
            #Write First list of data to heading 1 (orgList)
    gw.writerows([orgList[item]] for item in column)
            #For each value in new integer list, add row to CSV
    for val in newList:
        gw.writerow([val])

Answer 1

未经测试：

import csv
from itertools import izip_longest

some_ints = [1,0,1,2,1,2,1,1]

with open('input') as fin, open('output', 'w') as fout:
    csvin = csv.reader(fin)
    csvout = csv.writer(fout)
    cols = izip_longest(csvin, some_ints, fillvalue='')
    csvout.writerows(cols)

Answer 2

你遇到了两个相关的问题：

• 你在读取的同时又在写入同一个文件
• 你只想输出新数据，而不是包含新旧数据的新行。

首先，把数据读到内存中：

with open(r'C:\Data.csv','rb') as f:
    rows = list(csv.reader(f))

然后把元组列表转换成一个新的元组列表，里面包含新数据：

newdata = [1,0,1,2,1,2,1,1]
newrows = [rows[0]]            # keep the current two headers
newrows += izip_longest(rows[1:], newdata, fillvalue=0)

最后，把数据写回到磁盘上：

with open(r'C:\Data.csv', 'wb') as f:
     csv.writer(f).writerows(newrows)

Answer 3

这里有一段代码，可以修复这个错误：

import csv
from itertools import izip_longest


# Creating a CSV file
with open(r'Data.csv','wb') as f:
    fw = csv.writer(f)
    fw.writerows( (('Heading 1', 'Heading 2'),
                   ('1'),
                   ('1'),
                   ('0'),
                   ('2'),
                   ('1'),
                   ('0'))   )


print "The CSV file at start, read by a csv.reader :\n"
with open(r'Data.csv','rb') as f:
    fr = csv.reader(f)
    print '\n'.join(map(repr,fr))


print '\n------------------------------------------'
newdata = [10,0,10,20,10,20,10,10]

with open(r'Data.csv','rb') as f:
    fr = csv.reader(f)
    newrows = [fr.next()]
    newrows += (a+[b] for a,b in izip_longest(fr, newdata,
                                              fillvalue=[0]))

print 'newrows\n',newrows

with open(r'Data.csv', 'wb') as f:
     csv.writer(f).writerows(newrows)
print '------------------------------------------\n'


print "The new CSV file created, read by a csv.reader :\n"
with open(r'Data.csv','rb') as f:
    fr = csv.reader(f)
    print '\n'.join(map(repr,fr))

它会显示：

The CSV file at start, read by a csv.reader :

['Heading 1', 'Heading 2']
['1']
['1']
['0']
['2']
['1']
['0']

------------------------------------------
newrows
[['Heading 1', 'Heading 2'], ['1', 10], ['1', 0], ['0', 10], ['2', 20], ['1', 10], ['0', 20], [0, 10], [0, 10]]
------------------------------------------

The new CSV file created, read by a csv.reader :

['Heading 1', 'Heading 2']
['1', '10']
['1', '0']
['0', '10']
['2', '20']
['1', '10']
['0', '20']
['0', '10']
['0', '10']

编辑

更加简洁

import csv
from itertools import izip_longest
from os import remove,rename

# Creating a CSV file
with open(r'Data.csv','wb') as f:
    fw = csv.writer(f)
    fw.writerows( (('Heading 1', 'Heading 2'),
                   ('1'),
                   ('1'),
                   ('0'),
                   ('2'),
                   ('1'),
                   ('0'))   )

print "The CSV file at start, read by a csv.reader :\n"
with open(r'Data.csv','rb') as f:
    print '\n'.join(map(repr,csv.reader(f)))


#------------------------------------------
newdata = [10,0,10,20,10,20,10,10]

with open(r'Data.csv','rb') as f, open(r'newData.csv','wb') as g:
    fr = csv.reader(f)
    gw = csv.writer(g)
    gw.writerow(fr.next())
    gw.writerows( a+[b] for a,b in izip_longest(fr, newdata,
                                                fillvalue=[0]) )
remove (r'Data.csv')
rename (r'newData.csv',r'Data.csv')

#------------------------------------------

print "The new CSV file created, read by a csv.reader :\n"
with open(r'Data.csv','rb') as f:
    print '\n'.join(map(repr,csv.reader(f)))