将 io.StringIO 转换为 io.BytesIO [英] convert io.StringIO to io.BytesIO

问题描述

原始问题:我得到了一个 StringIO 对象，我如何将其转换为 BytesIO?

original question: i got a StringIO object, how can i convert it into BytesIO?

更新:更普遍的问题是，如何转换二进制(编码)file-like 对象被解码为 python3 中的类文件 对象?

update: The more general question is, how to convert a binary (encoded) file-like object into decoded file-like object in python3?

我得到的天真的方法是:

the naive approach i got is:

import io
sio = io.StringIO('wello horld')
bio = io.BytesIO(sio.read().encode('utf8'))
print(bio.read())  # prints b'wello horld'

有没有更高效、更优雅的方式来做到这一点?上面的代码只是将所有内容读入内存，对其进行编码，而不是分块流式传输数据.

is there more efficient and elegant way of doing this? the above code just reads everything into memory, encodes it instead of streaming the data in chunks.

例如，对于反向问题 (BytesIO -> StringIO)，存在一个类 - io.TextIOWrapper 就是这样做的(见这个答案)

for example, for the reverse question (BytesIO -> StringIO) there exist a class - io.TextIOWrapper which does exactly that (see this answer)

推荐答案

有趣的是，尽管这个问题看似合理，但要找出我需要转换 StringIOStringIO 的实际原因并不容易code> 转换为 BytesIO.两者基本上都是缓冲区，您通常只需要其中一个就可以对字节或文本进行一些额外的操作.

It's interesting that though the question might seem reasonable, it's not that easy to figure out a practical reason why I would need to convert a StringIO into a BytesIO. Both are basically buffers and you usually need only one of them to make some additional manipulations either with the bytes or with the text.

我可能错了，但我认为您的问题实际上是如何使用 BytesIO 实例，当您要传递给它的某些代码需要一个文本文件时.

I may be wrong, but I think your question is actually how to use a BytesIO instance when some code to which you want to pass it expects a text file.

在这种情况下，这是一个常见问题，解决方案是 codecs模块.

In which case, it is a common question and the solution is codecs module.

使用它的两种常见情况如下:

The two usual cases of using it are the following:

In [16]: import codecs, io

In [17]: bio = io.BytesIO(b'qwe\nasd\n')

In [18]: StreamReader = codecs.getreader('utf-8')  # here you pass the encoding

In [19]: wrapper_file = StreamReader(bio)

In [20]: print(repr(wrapper_file.readline()))
'qwe\n'

In [21]: print(repr(wrapper_file.read()))
'asd\n'

In [26]: bio.seek(0)
Out[26]: 0

In [27]: for line in wrapper_file:
    ...:     print(repr(line))
    ...:
'qwe\n'
'asd\n'

编写要写入的文件对象

In [28]: bio = io.BytesIO()

In [29]: StreamWriter = codecs.getwriter('utf-8')  # here you pass the encoding

In [30]: wrapper_file = StreamWriter(bio)

In [31]: print('жаба', 'цап', file=wrapper_file)

In [32]: bio.getvalue()
Out[32]: b'\xd0\xb6\xd0\xb0\xd0\xb1\xd0\xb0 \xd1\x86\xd0\xb0\xd0\xbf\n'

In [33]: repr(bio.getvalue().decode('utf-8'))
Out[33]: "'жаба цап\\n'"

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