python加减乘除，格式化字符串

#!/usr/bin/python
num1 = input("Please input a number:")
num2 = input("Please input a number:")
print num1 + num2
print num1 - num2
print num1 * num2
print num1 / num2
print "%s + %s =  %s" % (num1, num2, num1 + num2)
print "%s - %s =  %s" % (num1, num2, num1 - num2)
print "%s * %s =  %s" % (num1, num2, num1 * num2)
print "%s / %s =  %s" % (num1, num2, num1 / num2)


/除
//取整
%取余
**乘方


#!/usr/bin/env python


from operator import add, sub,mul,div, imod


from random import randint, choice


ops = {'+': add, '-': sub, '*': mul, '/': div} 
ops1 = {'+': add, '-': sub, '*': mul} 
MAXTRIES = 2
def doprob():
    nums = [randint(1,10) for i in range(2)]
    nums.sort(reverse=True)
    if  imod(*nums) == 0:
        op = choice('+-*/')
        ans=ops[op](*nums)
    else:
        op = choice('+-*')
        ans=ops1[op](*nums)
    pr='%d %s %d =' % (nums[0],op,nums[1])   
    oops = 0 
    while True:
        try:
            if int(raw_input(pr))==ans:
                print 'correct!'
                break
            if oops == MAXTRIES:
                print 'answer \n%s%d' %(pr,ans)
            else:
                print 'incorrect... try again'  
                oops+=1
        except(KeyboardInterrupt,EOFError,ValueError):   
             print 'invalid input... try again'
def main():
    while True:
        doprob()   
        try:
            opt = raw_input('again?[y]').lower()   
            if opt and opt[0]=='n':
                break
        except (KeyboardInterrupt,EOFError):
            break
if __name__=='__main__': 
    main()