四则运算作业

代码：
# -*- coding: utf-8 -*-
import random
from fractions import Fraction
from envs.py3k.Lib.symbol import except_clause
print ("小学四则运算测试：(结果保留1位有效数字)")
ops = ['+', '-', '*', '/']  # 锟斤拷锟斤拷锟�
ans = ""   # 锟矫伙拷锟截达拷
num = 1    # 锟斤拷锟�
rightnum = 0
t = 0
while(1):
    try:
        while(1):
            a = input("是否答题（退出请输入q或Q，否则按Enter键）")
            if a not in ['q','Q']:
                add1 = random.randint(1, 100)  # 锟斤拷1
                add2 = random.randint(1, 100)  # 锟斤拷2
                op = random.randint(0, 3)      # 锟斤拷锟斤拷锟斤拷锟斤拷
                eq = str(add1) + ops[op] + str(add2) 
                val = round(eval(eq),1)                       # 锟斤拷式锟斤拷
 
                print ("Q%d: %s=" %(num,eq))      # 锟斤拷锟斤拷锟斤拷锟�
 
                ans = input("A%d: "%num)        # 锟矫伙拷锟截达拷
                if val == eval(ans):     # 锟斤拷确
                    rightnum += 1
                    print ("right!")
                else:                     # 锟斤拷锟斤拷
                    print ("error. the right answer is %f" % val)
                num += 1                  # 锟斤拷锟斤拷锟斤拷锟�
                t +=1
            else:
                print("right:%d" %rightnum)       # 锟剿筹拷循锟斤拷
                print("all:%d" %num)
                s=round(rightnum/num,3)
                print("正确率%f" %s)
                break
    except:
        print("输入错误")
    if a in ['q','Q']:
        break