tzinfo.py 文件源码

def memorized_datetime(seconds):
    '''Create only one instance of each distinct datetime'''
    try:
        return _datetime_cache[seconds]
    except KeyError:
        # NB. We can't just do datetime.utcfromtimestamp(seconds) as this
        # fails with negative values under Windows (Bug #90096)
        dt = _epoch + timedelta(seconds=seconds)
        _datetime_cache[seconds] = dt
        return dt