Unable to pass inputs to stdin of Python subprocess

Question

Unable to pass inputs to stdin of subprocess. Terminal gets struck while waiting for input. How can I handle stdin properly?

def run_command(command: str, out_callback, in_callback):

    process = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)

    while process.poll() is None:
        if process.stdout:
            # On Output
            for line in process.stdout:
                out_callback(line.strip())

        if process.stderr:
            # On Error
            for line in process.stderr:
                out_callback(line.strip())

        if process.stdin:
            # On Input !!! This doesnt works !!!
            input = in_callback()
            process.stdin.write(input.encode())
            process.stdin.flush()

        # On Termination
        out_callback(process.returncode)