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'