def freeze(h, output_yaml, resolve, groups):
    """Output installed packages."""
    if not groups:
        groups = filter(lambda group: not group.lower().startswith("bower"),
                        h.requirements.keys())
    else:
        groups = [text_type.strip(group) for group in groups.split(",")]

    if output_yaml:
        for requirements in h.requirements.values():
            for requirement in requirements:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
        click.echo(h.requirements.yaml)
    else:
        for group in groups:
            if not h.requirements[group]:
                continue
            click.echo("# {}".format(group))
            for requirement in h.requirements[group]:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
                click.echo(str(requirement))
def _get_or_create_cached_value(self, key, getter, ttl=None):
        # happy path
        try:
            expiry, value = self._cache[key]
        except KeyError:
            pass
        else:
            if expiry is None or time.time() < expiry:
                logger.debug("Key %s from cache", key)
                return value
            logger.debug("Cache for key %s has expired", key)

        # get value
        value = getter()
        if ttl:
            expiry = time.time() + ttl
        else:
            expiry = None
        self._cache[key] = (expiry, value)
        logger.debug("Set cache for key %s", key)

        return value