python - 如何将字符串附加到django模型中的主键

Question

我想区分一些本地数据和远程数据..所以我想让本地数据的主键类似于：local_1，local_2...等。

我的模型是：

class coupon(models.Model):

    success = models.IntegerField()                      # Count of the number of times people have made it work
    failure = models.IntegerField()                      # Count of the number of times this has failed    
    couponDescription = models.TextField()               # Coupon Description
    active =  models.BooleanField(default=True)
    couponCode = models.CharField(max_length=30)
    couponStore = models.CharField(max_length=30)        # Store Name
    featured =  models.BooleanField(default=False)
    couponTitle = models.CharField(max_length=100)       # Coupon Title
    updatedAt = models.DateTimeField(auto_now=True)
    createdAt = models.DateTimeField(auto_now=True)
    lastTested = models.DateField(auto_now_add=True)     # When was the coupon last tested
    localCouponId = models.CharField(max_length=30,primary_key=True)

那么我如何使用与...1,2,3,4....等整数连接localCouponId的字符串进行自动递增。local_