python Read all available data from subprocess.PIPE but do not block

Question

Having a simple subprocess example.

import subprocess
sshProcess = subprocess.Popen(['ssh','localhost','/usr/local/bin/fish'],
                               stdin=subprocess.PIPE, 
                               stdout=subprocess.PIPE,
                               universal_newlines=True,
                               errors='ignore',
                               bufsize=0)
sshProcess.stdin.write("echo 124\n")

sshProcess.stdin.close()
print(sshProcess.stdout.read(end=""))

The same but with stdin.close() after stdout.read() will block for ever.

print(sshProcess.stdout.read(end=""))
sshProcess.stdin.close()

I would like to read() data till it is available and do not block.
Similar question Non-blocking read on a subprocess.PIPE in python has very complicated answers. Does Python have such a simple mechanisms as POSIX to check how much data available in fd?

POSIX C

int bytes_available;
ioctl(fd, FIONREAD, &bytes_available);