How to set sys.stdout encoding in Python 3?

Question

Setting the default output encoding in Python 2 is a well-known idiom:

sys.stdout = codecs.getwriter("utf-8")(sys.stdout)

This wraps the sys.stdout object in a codec writer that encodes output in UTF-8.

However, this technique does not work in Python 3 because sys.stdout.write() expects a str, but the result of encoding is bytes, and an error occurs when codecs tries to write the encoded bytes to the original sys.stdout.

What is the correct way to do this in Python 3?

Answer 1

Python 3.1 added io.TextIOBase.detach(), with a note in the documentation for sys.stdout:

The standard streams are in text mode by default. To write or read binary data to these, use the underlying binary buffer. For example, to write bytes to stdout, use sys.stdout.buffer.write(b'abc'). Using io.TextIOBase.detach() streams can be made binary by default. This function sets stdin and stdout to binary:

def make_streams_binary():
    sys.stdin = sys.stdin.detach()
    sys.stdout = sys.stdout.detach()

Therefore, the corresponding idiom for Python 3.1 and later is:

sys.stdout = codecs.getwriter("utf-8")(sys.stdout.detach())