Python:没有 csv.close()? [英] Python: No csv.close()?

问题描述

我正在使用 CSV 模块来读取制表符分隔的文件.代码如下:

I'm using the CSV module to read a tab delimited file. Code below:

z = csv.reader(open('/home/rv/ncbi-blast-2.2.23+/db/output.blast'), delimiter='	')

但是当我将 Z.close() 添加到我的脚本末尾时，我收到错误消息，指出csv.reader' 对象没有属性 'close'"

But when I add Z.close() to end of my script i get and error stating "csv.reader' object has no attribute 'close'"

z.close()

那么我如何关闭Z"?

推荐答案

阅读器实际上只是一个解析器.当您要求它提供一行数据时，它会将读取操作委托给底层的 file 对象，并将结果转换为一组字段.阅读器本身不管理任何使用完后需要清理的资源，因此无需关闭它；这将是一个毫无意义的操作.

The reader is really just a parser. When you ask it for a line of data, it delegates the reading action to the underlying file object and just converts the result into a set of fields. The reader itself doesn't manage any resources that would need to be cleaned up when you're done using it, so there's no need to close it; it'd be a meaningless operation.

你应该确保关闭底层的 file 对象，因为它确实管理一个需要清理的资源(一个打开的文件描述符).方法如下:

You should make sure to close the underlying file object, though, because that does manage a resource (an open file descriptor) that needs to be cleaned up. Here's the way to do that:

with open('/home/rv/ncbi-blast-2.2.23+/db/output.blast') as f:
    z = csv.reader(f, delimiter='	')
    # do whatever you need to with z

如果您不熟悉 with语句，大致相当于将其内容包含在 try...finally 块中，该块在 finally 部分关闭文件.

If you're not familiar with the with statement, it's roughly equivalent to enclosing its contents in a try...finally block that closes the file in the finally part.

希望这无关紧要(如果确实如此，您确实需要更新到更新版本的 Python)，但是 with 语句是在 Python 2.5 中引入的，并且在该版本中您需要一个 __future__ 导入来启用它.如果您使用的是更旧版本的 Python，则必须使用 try...finally 自行关闭.

Hopefully this doesn't matter (and if it does, you really need to update to a newer version of Python), but the with statement was introduced in Python 2.5, and in that version you would have needed a __future__ import to enable it. If you were working with an even older version of Python, you would have had to do the closing yourself using try...finally.

^{感谢 Jared 指出与 with 声明的兼容性问题.}

^{Thanks to Jared for pointing out compatibility issues with the with statement.}

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