convert io.StringIO to io.BytesIO

Question

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

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

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'

is there more elegant way of doing this?

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

Answer 1

有趣的是，尽管这个问题看似合理，但要找出将a转换StringIO为a 的实际原因并不是一件容易的事BytesIO。两者基本上都是缓冲区，通常只需要其中一个就可以对字节或文本进行一些其他操作。

我可能是错的，但是我认为您的问题实际上是BytesIO当要传递给它的某些代码需要文本文件时，如何使用实例。

在这种情况下，这是一个常见问题，解决方案是编解码器模块。

以下是使用它的两种常见情况：

撰写要读取的文件对象

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('????', '???', 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]: "'???? ???\\n'"