python以文本方式字节流,如何在Python 3中将文本流编码为字节流？

Decoding a byte stream into a text stream is easy:

import io

f = io.TextIOWrapper(io.BytesIO(b'Test\nTest\n'), 'utf-8')

f.readline()

In this example, io.BytesIO(b'Test\nTest\n') is a byte stream and f is a text stream.

I want to do exactly the opposite of that. Given a text stream or file-like object, I would like to encode it into a byte stream or file-like object without processing the entire stream.

This is what I've tried so far:

import io, codecs

f = codecs.getreader('utf-8')(io.StringIO('Test\nTest\n'))

f.readline()

# TypeError: can't concat str to bytes

f = codecs.EncodedFile(io.StringIO('Test\nTest\n'), 'utf-8')

f.readline()

# TypeError: can't concat str to bytes

f = codecs.StreamRecoder(io.StringIO('Test\nTest\n'), None, None,

codecs.getreader('utf-8'), codecs.getwriter('utf-8'))