如何用python写回打开的csv文件

Question

我试图浏览一个csv文件，验证邮政编码，并将城市和州写入csv文件的最后一列。在

我设法得到了csv数据并得到了城市和州，但我不知道如何将新数据写入最后一列。{a1}但不显示如何创建一个csv。在

以下是我目前为止的代码：

with open("propertyOutput.csv", "rbw") as fp:
    reader = csv.DictReader(fp, skipinitialspace=True)
    table = [row for row in reader]
    for rows in table:
        stringNeed = rows['zip']
        if not stringNeed.isdigit(): 
            print"not number"  #would like to write this to the column
            pass
        else:
            if not len(stringNeed) == 5:  
                print"string not 5 long"  # would like to write this to the column
            else:
                x = getCityState(stringNeed)
                print x  # would like to write this to the column

Answer 1

一般来说，文件不支持“插入”的概念。您只能删除它们、覆盖它们（也就是说，要么完全替换文件，要么用完全相同（不同）字节数替换一定数量的字节），或者附加到它们。在

因此，要更改CSV文件的内容，您必须重写它（好消息是，CSV模块使它非常容易）。在

Answer 2

您需要分两步来完成：

1. 读取csv文件并存储信息

   import csv
   
   with open("propertyOutput.csv", "rbw") as fp:
       reader = csv.DictReader(fp, skipinitialspace=True)
       table = [row for row in reader]
       header = reader.fieldnames 
   

2. 将信息写入新文件或替换旧文件

   with open("propertyOutput.csv", "wb") as fp:
       writer = csv.DictWriter(fp, header)
       for row in table:
           if not stringNeed.isdigit(): 
               rows['zip'] = "not number"
           # even more stuff to check and edit here
           # write the edited row
           writer.writerow(row)