def number_to_digits(num):
    digits = []
    while num:
        digits.append(num % 10)
        num /= 10
    return digits[::-1]
def digits_to_number(digits):
    return sum([x*10**i for i, x in enumerate(reversed(digits))])
    
num = 12345
print 3 in number_to_digits(num**2)
print digits_to_number(number_to_digits(num)[::-1])
number = number_to_digits(num)
number[0], number[-1] = number[-1], number[0]
print digits_to_number(number)

def number_to_digits(num):
    digits = []
    while num:
        digits.append(num % 10)
        num //= 10
    return digits[::-1]
def digits_to_number(digits):
    return sum([x*10**i for i, x in enumerate(reversed(digits))])
    
num = 12345
print(3 in number_to_digits(num**2))
print(digits_to_number(number_to_digits(num)[::-1]))
number = number_to_digits(num)
number[0], number[-1] = number[-1], number[0]
print(digits_to_number(number))