On Fri, Sep 5, 2014 at 9:48 AM, Seymore4Head <Seymore4Head@hotmail.invalid> wrote:
> 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" > > One neat feature of Python is the for...else function. The code inside the else block will run only if the loop ran to completion (untested code follows): 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 else: print("Number is prime") wait = input (" "*40 + "Wait") Depending on how advanced you want to get (I know you are relatively new to Python), another decent way would be to extract the prime check to a function, and return the result, and print based on that result (again, untested code): def isPrime(number): for x in range(2,a): if a%x==0: return False return True while True: a=random.randrange(1,8) print (a) if isPrime(a): print("Number is prime") else: print("Number is not prime") wait = input (" "*40 + "Wait")
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