How can I write bytes to a file in Python 3 without knowing the encoding?

In Python 2.x with 'file-like' object:

sys.stdout.write(bytes_)
tempfile.TemporaryFile().write(bytes_)
open('filename', 'wb').write(bytes_)
StringIO().write(bytes_)

How can I do the same in Python 3?

How can I write equivalent of the following Python 2.x code?

def write(file_, bytes_):
    file_.write(bytes_)

Note: sys.stdout is not always semantically a text stream. It might be beneficial to consider it as a stream of bytes sometimes. For example, make encrypted archive of dir/ on remote machine:

tar -c dir/ | gzip | gpg -c | ssh user@remote 'dd of=dir.tar.gz.gpg'

There is no point to use Unicode in this case.