Xonsh formatter dict: last return code, duration of last command

prompt_return_code.py

last_duration = last_return = 0
orig_append = __xonsh_history__.append

def append(cmd):
    nonlocal last_duration, last_return
    last_return = cmd['rtn']
    a, b = cmd['ts']
    last_duration = b - a
    orig_append(cmd)
__xonsh_history__.append = append

def fmt_last_duration():
    nonlocal last_duration
    if last_duration >= 60:
        d = round(last_duration)
        result = '{}:{:02}'.format(d//60, d%60)
    elif last_duration >= 1:
        result = '{:.1f}'.format(last_duration)
    else:
        return
    last_duration = 0
    return result

def fmt_last_return():
    nonlocal last_return
    if last_return:
        result = str(last_return)
        last_return = 0
        return result