chosen_exit.py

def close_all_circuits(ctrl):
    circuits = ctrl.get_circuits()
    for c in circuits:
        ctrl.close_circuit(c.id)

def initialize(ctrl):
    # don't create circuits automatically
    ctrl.set_conf('__DisablePredictedCircuits', '1')

    # close all existing circuits
    close_all_circuits(ctrl)

    # find a valid first hop
    initial_hop = None
    guards = ctrl.get_info('entry-guards')
    for guard in guards.splitlines():
        guard = guard.strip()
        parts = guard.split()
        if len(parts) < 2:
            continue
        if parts[1] != 'up':
            continue
        initial_hop = parts[0].split('~')[0]
        break

    if not initial_hop:
        sys.exit("cannot find valid first hop")

    return initial_hop

def use_exit(ctrl, initial_hop, ex):
    try:
        close_all_circuits(ctrl)
    except:
        pass

    try:
        ex_ns = ctrl.get_network_status(ex)
    except stem.DescriptorUnavailable:
        raise  # handle offline node

    fp = ex_ns.fingerprint

    if stem.Flag.RUNNING not in ex_ns.flags:
        return  # handle offline node
    
    if stem.Flag.EXIT not in ex_ns.flags:
        return  # node's not exit anymore

    circ_id = ctrl.new_circuit([initial_hop, fp])
    # use the circuit

    try:
        ctrl.close_circuit(circ_id)
    except:
        raise  # handle issues
        
first_hop = initialize(ctrl)
use_exit(ctrl, first_hop, chosen_exit)