My backwards logic

[Seymore4Head]

I'm still doing practice problems.  I haven't heard from the library
on any of the books I have requested.

http://www.practicepython.org/exercise/2014/04/16/11-check-primality-functions.html

This is not a hard problem, but it got me to thinking a little.  A
prime number will divide by one and itself.  When setting up this
loop, if I start at 2 instead of 1, that automatically excludes one of
the factors.  Then, by default, Python goes "to" the chosen count and
not "through" the count, so just the syntax causes Python to rule out
the other factor (the number itself).

So this works:
while True:
    a=random.randrange(1,8)
    print (a)
    for x in range(2,a):
        if a%x==0:
            print ("Number is not prime")
            break
    wait = input (" "*40  + "Wait")

But, what this instructions want printed is "This is a prime number"
So how to I use this code logic NOT print (not prime) and have the
logic print "This number is prime"