status = models.CharField(max_length=2, null=True, choices=STATUSES, default='E')
or to avoid setting an invalid default if STATUSES changes:
status = models.CharField(max_length=2, null=True, choices=STATUSES, default=STATUSES[0][0])
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…