Assign username to field in table

Let’s say I have a Table1 that contains 5 data,

class Table1(models.Model):
    code     = models.CharField(max_length=16,unique=True)

    author_Up    = models.CharField(max_length=16,default=User)
    date_Up      = models.DateTimeField(auto_now=True)
    post_date    = models.DateTimeField(
    author       = models.ForeignKey(User,on_delete=models.CASCADE)
    def __str__(self):
        return self.code

I am using as:

class Table1_F(forms.ModelForm):
    code        = forms.CharField(label='Code',max_length=16)
    class Meta:
        model= Table1

The Problem is I need to assign a new values of (author_Up) and (date_Up) every time that another user make an update and keep the initial author.

How do I solve this Please?

problem solved in this link

stackoverflow Solving links