Constants from the module¶

A script has no closure: the body runs on the server, where nothing from your Python process exists. A module-level constant is the exception worth making, because it is already a literal and can simply be folded in.

SESSION_TTL_SECONDS = 30 * 60


@script
def touch_session(session: Key) -> int:
    hits = redis.incr(session)
    redis.expire(session, SESSION_TTL_SECONDS)  # -> redis.call('EXPIRE', session, 1800)
    return hits

int, float, str, bytes and bool are folded, including through a dotted name — an IntEnum member, or an attribute of a settings object. Anything else is refused with the same caret as everything else, because there is no literal to fold:

'SESSION_TTL' is a module-level timedelta, which has no Lua literal
  File "/srv/app/sessions.py", line 18
    redis.expire(session, SESSION_TTL)
                          ^
  hint: Only an int, float, str, bytes or bool constant is folded into the
  script. Pass anything else as an argument, or name the literal it reduces to.