Question

我有两个文件，第一个叫做book1.csv，看起来像这样：

 header1,header2,header3,header4,header5
 1,2,3,4,5
 1,2,3,4,5
 1,2,3,4,5

第二个文件名为book2.csv，如下所示：

 header1,header2,header3,header4,header5
 1,2,3,4
 1,2,3,4
 1,2,3,4

我的目标是将book1.csv中包含5的列复制到book2.csv中的相应列。

我的代码的问题似乎是它没有正确附加，也没有选择我想要复制的索引。它还给出了一个错误，我选择了一个不正确的索引位置。输出如下：

 header1,header2,header3,header4,header5
 1,2,3,4
 1,2,3,4
 1,2,3,41,2,3,4,5

这是我的代码：

 import csv

 with open('C:/Users/SAM/Desktop/book2.csv','a') as csvout:
    write=csv.writer(csvout, delimiter=',')
    with open('C:/Users/SAM/Desktop/book1.csv','rb') as csvfile1:
        read=csv.reader(csvfile1, delimiter=',')
        header=next(read)
        for row in read:
            row[5]=write.writerow(row)

我该怎么做才能让它正确追加？

感谢您的帮助！

Answer 1

这样的事情怎么样？我在两本书中都读过，将book1的最后一个元素附加到book2行book2中的每一行，我将其存储在列表中。然后我将该列表的内容写入新的.csv文件。

with open('book1.csv', 'r') as book1:
    with open('book2.csv', 'r') as book2:
        reader1 = csv.reader(book1, delimiter=',')
        reader2 = csv.reader(book2, delimiter=',')

        both = []
        fields = reader1.next() # read header row
        reader2.next() # read and ignore header row
        for row1, row2 in zip(reader1, reader2):
            row2.append(row1[-1])
            both.append(row2)

        with open('output.csv', 'w') as output:
            writer = csv.writer(output, delimiter=',')
            writer.writerow(fields) # write a header row
            writer.writerows(both)

Answer 2

关于“我选择了错误的索引位置的错误”，我怀疑这是因为您在代码中使用了row[5]。 Python中的索引从0开始，所以如果你有A = [1, 2, 3, 4, 5]然后获得5，那么你将print(A[4])。

假设两个文件的行数相同且行的顺序相同，我想你想做这样的事情：

import csv
# Open the two input files, which I've renamed to be more descriptive,
# and also an output file that we'll be creating
with open("four_col.csv", mode='r') as four_col, \
     open("five_col.csv", mode='r') as five_col, \
     open("five_output.csv", mode='w', newline='') as outfile:
  four_reader = csv.reader(four_col)
  five_reader = csv.reader(five_col)
  five_writer = csv.writer(outfile)
  _ = next(four_reader) # Ignore headers for the 4-column file
  headers = next(five_reader)
  five_writer.writerow(headers)
  for four_row, five_row in zip(four_reader, five_reader):
    last_col = five_row[-1] # # Or use five_row[4]
    four_row.append(last_col)
    five_writer.writerow(four_row)

Answer 3

尽管上面的一些代码可行，但它并不是真正可扩展的，需要一种矢量化方法。与numpy或pandas一起工作将使这些任务变得更容易，因此学习它有点好。

您可以从Pandas Website

下载pandas

# Load Pandas
from pandas import DataFrame

# Load each file into a pandas dataframe, this is based on a numpy array
data1 = DataFrame.from_csv('csv1.csv',sep=',',parse_dates=False)
data2 = DataFrame.from_csv('csv2.csv',sep=',',parse_dates=False)

#Now add 'header5' from data1 to data2
data2['header5'] = data1['header5']

#Save it back to csv
data2.to_csv('output.csv')

Answer 4

为什么不逐行读取文件并使用-1索引查找最后一项？

endings=[]

with open('book1.csv') as book1:
   for line in book1:        
      # if not header line:  
      endings.append(line.split(',')[-1])

linecounter=0
with open('book2.csv') as book2:
   for line in book2:
      # if not header line:
      print line+','+str(endings[linecounter]) # or write to file
      linecounter+=1

如果行号不匹配，您还应该发现错误。

复制CSV文件的一列，并使用python将其添加到另一个文件

4 个答案: