Prime Number Finder (FIX!)

from time import time,ctime,sleep

DBFILE="primesDB.txt"
primes=[2,5]    #Not found by fastPrime(n) because of a speed optimization
autosv=1000000  #Autosave not included this paste

#
# LOAD FROM DATABASE DISABLED!
#

def isprime(n): ## For imports for example?
    if n < 2: return str(n)+" is not a prime number."
    if n == 2: return str(n)+" is a prime number."
    for i in [2]+range(3,int(n**0.5)//1+1,2):
        if not n%i:
            return "%i is %i*%i"%(n,i,n/i)
    else:
        return "%i is not a prime number."%(n)
    return "%i is a prime number."%(n)

def fastPrime(n):
    if n%10 in [1,3,7,9]:
        for i in range(3,int(n**0.5)//1+1,2):
            if not n%i:
                #return "%i is %i*%i"%(n,i,n/i) #Slower
                return str(n)+" is "+str(i)+"*"+str(n/i)#Faster
    else:
        #return "%i is not a prime number."%(n) #Slower
        return str(n)+" is not a prime number."#Faster
    primes.append(n)
    #return "%i is a prime number."%(n) #Slower
    return str(n)+" is a prime number."#Faster

def check(start=3, end=1000000):
    s=time()
    if start<3:
        start=3
    if end<start:
        end=1000000
    for i in range(start,end):
        #curr=isprime(i)
        curr=fastPrime(i)
        if curr==str(i)+" is a prime number.":
            #print "Found a prime: %i; %s"%(i,ctime(time())) #SLOWER! In all programs that use a lot of string logic use string concat. instead of %x
            print "Found a prime: "+str(i)+"; "+ctime(time())
    print "Finished. Took %.2f seconds to finish."%(time()-s)

if __name__=="__main__":
    print "Tip: '-1' to ignore (Replaced by defaults: Start=3, End=1000000)."
    check(input("Start at which number?"),input("End at which number?"))
    print "Primes total found: %i"%(len(primes))
    print "Pre-save..."
    p=[]
    for i in primes:
        p.append(str(i))
    sv="\n".join(p)
    with open(DBFILE,"w") as f:
        print "Saving..."
        f.write(sv)
        print "Saved!"

    raw_input("Enter to continue...")