Python - Determine Primality of a number

 
# Determining primality by using a simple trial division test. 
# 
# This approach tests whether n is a multiple of an integer i 
# between 2 and √n.  If it is a multiple of any of these integers 
# then it is not a prime. 
 
import math
import time
 
def isPrime(n):
    for i in range(2, int(math.sqrt(n))):
        if n % i == 0:
            return False
    return True
 
def withTimer(n):
    start = time.time()
    prime = isPrime(n)
    elapsed = time.time() - start
    print("{0}   {1}    time:{2}").format(prime, n, elapsed)
 
# Primality of 2 to 13 digit known primes 
withTimer(13)
withTimer(715827883)
withTimer(2932031007403)
 
# test non primes 
withTimer(52)
withTimer(5820384023)
withTimer(2059384726303)
 
# my output: 
# True   13    time:0.0 
# True   715827883    time:0.00300002098083 
# True   2932031007403    time:0.521000146866 
# False   52    time:0.0 
# False   5820384023    time:0.000999927520752 
# False   2059384726303    time:0.029000043869 
 
 
 

Python - limit cpu percentage for script

# It is sometimes useful to monitor how much cpu time or 
# cpu percentage your script is consuming. 
# This script will limit the cpu usage of your script 
 
# This example demostrates how to calculate the system 
# and user cpu time and cpu percentage 
 
# Note: this example is in python 3.0 
#   however, it is easily ported back to 2.x 
#   by replaceing print() with print 
 
import os
import time
 
def getPercentage(unew, uold, start):
    """ 
    calculate the percentage of cpu time 
    """ 
    return 100 * (float(unew) - float(uold)) / (time.time()-float(start))
 
def looper(timeCount, percentageGoal):
    """ 
    loop over many tasks and keep the total cpu percentage 
    consumtion to a desired level 
    """ 
    start = time.time()
    time.sleep(0.1)
    keepLooping = True
    uold, sold, cold, c, e = os.times()
    percentage = 0.0
    while keepLooping:
        unew, snew, cnew, c, e = os.times()
        # since we are calculating the times from before we started looping the 
        # percentages will be averaged over the duration of the script. 
        print ("user %", percentage)
 
        # This just toggles to stop looping 
        # when a time has been reached. In a real 
        # script you would check for more work and 
        # toggle off when there is no more work to 
        # be done. 
        if time.time()-start > timeCount:
            keepLooping = False
        #else: 
        #    print( time.time()-start) 
 
        # do work: 
        #   In order for this script to actually help limit 
        #   the cpu usage you would need to break your script into 
        #   sections. 
        #   For example: if you were going to iterate through a large 
        #       list of data and perform actions on the contents 
        #       of the list then you should perform on action here 
        #       and keep looping through until all the actions 
        #       are accomplished. 
        # 
        # in this case we're just eating cpu so we get some numbers 
        print("do work...")
        for i in range(1,1000000):
            b = 8*342*i*234
 
        # tone back cpu usage 
        while True:
            percentage = getPercentage(unew, uold, start)
            if percentage > percentageGoal:
                time.sleep(0.1)
            else:
                break;
 
if __name__ == '__main__':
    # loop through work (for 4 seconds) and keep the cpu % 
    # to less than 30% 
    looper(4, 30)
 
## my output: 
##      user % 0.0 
##      do work... 
##      user % 0.0 
##      do work... 
##      user % 29.6673831301 
##      do work... 
##      user % 29.1137166495 
##      do work... 
##      user % 29.7617156875 
##      do work... 
##      user % 29.5707887319 
##      do work... 
##      user % 29.8122197706 
##      do work... 
##      user % 29.3053848216 
##      do work... 
##      user % 29.9385051866 
##      do work...