在python中写入csv文件（文件在操作结束时留空） [英] Writing csv files in python (Files are left blank at the end of the operation)

问题描述

我在python写csv，我想知道为什么我的输出文件是空白的，当程序完成运行。首先，这里是我的代码：

  reader = csv.reader（open（location，'rU'），delimiter =' ，'，quotechar =''）
 writer = csv.writer（open（'temp.csv'，'wb'），delimiter ='，'，quotechar =''）
 
 writer.writerow（[test，test，test，test，test，test，test]）
 
 count = 0 
对于读取器中的行：
如果count！= 0并且count< len（split）：
 writer.writerow（[row [0]，row [1]，row [2]，row [3]，row [4]，row [ ]）
 count = count + 1 
  

我知道了几件事： p>

• 程序完成后，写入temp.csv的所有内容都是测试行。


• 如果我在运行过程中强行停止程序，则实际上文本正在写入文件：因为某种原因它被擦除了。


• 我做了一些研究，很多人发现，关闭csv文件解决了他们的问题，但是这似乎并不适用于我，除非我缺少非常明显！

感谢您的帮助！

这里是一些更新的代码我正在使用：

  infile = open（location，'rU'）
 outfile = open（'temp.csv'，'wb'）
 reader = csv.reader（infile，delimiter ='，'，quotechar =''）
 writer = csv.writer（outfile，delimiter = '，'，'，quotechar =''）
 split = email_text.split（'NEW MESSAGE BEGINS HERE'）
 
 count = 0 
 for row in reader：
 if count！= 0 and count< len（split）：
 writer.writerow（[row [0]，row [1]，row [2]，row [3]，row [4]，row [ ]）
 outfile.flush（）
 count = count + 1 
 
 infile.close（）
 outfile.close（）
  

解决方案

您没有关闭文件。

使用上下文管理器：

如果你正在读文件p>

 打开（位置，'rU'）为infile，打开（'temp.csv'，'wb'）为outfile：
 reader = csv.reader（infile，delimiter ='，'，quotechar =''）
 writer = csv.writer（outfile，delimiter ='，'，quotechar =''）
 ... 
  

这将确保当 已退出（即使是由于异常）。

I am writing to csv in python, and I was wondering why my output files are blank when the program completes running. First off, here is my code:

reader = csv.reader(open(location, 'rU'), delimiter = ',', quotechar = '"')
writer = csv.writer(open('temp.csv', 'wb'), delimiter = ',', quotechar = '"')

writer.writerow(["test", "test", "test", "test", "test", "test", "test"])

count = 0
for row in reader:
    if count != 0 and count < len(split):
        writer.writerow([row[0], row[1], row[2], row[3], row[4], row[5], split[count-1]])
    count = count + 1

I know a few things about it:

• When the program finishes, all that is written to 'temp.csv' is the "test" line. The rest of the document is empty.
• If I force stop the program in the middle of running, there is in fact text being written to the file: it just gets wiped for some reason.
• I've done some research, and lots of people have found that "closing" the csv file solves their problems, but that doesn't seem to work for me, unless I am missing something obvious!

Thanks in advance for your help!

Edit: here is some updated code I am working with:

infile = open(location, 'rU')
outfile = open('temp.csv', 'wb')
reader = csv.reader(infile, delimiter = ',', quotechar = '"')
writer = csv.writer(outfile, delimiter = ',', quotechar = '"')
split = email_text.split('NEW MESSAGE BEGINS HERE')

count = 0
for row in reader:
    if count != 0 and count < len(split):
        writer.writerow([row[0], row[1], row[2], row[3], row[4], row[5], split[count-1]])
        outfile.flush()
    count = count + 1

infile.close()
outfile.close()

解决方案

You're not closing the file. While this may work fine if you're just reading a file, it's definitely not a good idea to do this when writing a file.

Use a context manager:

with open(location, 'rU') as infile, open('temp.csv', 'wb') as outfile:
    reader = csv.reader(infile, delimiter = ',', quotechar = '"')
    writer = csv.writer(outfile, delimiter = ',', quotechar = '"')
    ...

This ensures that the files will be closed when the with block is exited (even if it's because of an exception).

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