[Python] How to calculate the time variable and comapre a time data with the current time by...

For example, I have a model in models.py which looks like this:

class BlackList(models.Model):
username = models.CharField(max_length=1000)
flag1 = models.BooleanField(default=False)
trytologintime = models.DateTimeField(auto_now_add=True, null=True)


And in the views.py, what I try to do is something like this:

......
username = request.POST.get('username') # Get username input first
password = request.POST.get('password')
user = authenticate(request, username=username, password=password)
black_list_user = BlackList.objects.get(username=username)
# timenow = get time for now ( I do not know how to get it foe now )
passtime = timenow-black_list_user.trytologintime (Also do not know how to do the subtraction for time variable)
if passtime > 24 hr (How to compare the time)
black_list_user.flag1 = True
black_list_user.save()
......


My questions are:

1. How to get the current time?
2. How to do subtraction and compare two time variables?

Continue reading...