note 5 二分法求平方根，素数，回文数

+二分法求平方根

x = float(raw_input('Enter the number'))

low = 0

high = x

guess = (low + high ) / 2

if x < 0:

    print 'Number Error'

while abs(guess**2 - x) > 1e-5:

    if guess**2 < x:

        low = guess

    else:

        high = guess

    guess = (low + high) / 2

print 'The root of is',guess

+素数

前50个

 import math

 count = 0

 num = 2

 while count < 50:

     for i in range(2,int(math.sqrt(num)) + 1):

         if num % i == 0:

             break

         else:

             print x,'is a prime!'

             count += 1

        num += 1

+回文数

num = 12321

num_p = 0

num_temp = num

while num != 0:

    num_p = num_p * 10 + num % 10

    num /= 10

if num_temp == num_p:

    print 'OK'

else:

    print 'NO'