小学2年级数学混合运算手机打卡训练

import math
import random
score=0
num=eval(input("questions:"))
questions=[]
errors=[]
for i in range(num): 
    a=random.randint(2,9)
    b=random.randint(2,9)
    c=random.randint(2,9)
    op1=random.choice([' + ',' - '])
    op2=random.choice([' + ',' * ',' - ',' * '])
    exp= str(a) + op1 + str(b) + op2 + str(c)
    questions.append(exp)
for i in range(num):
    exp=questions[i]
    d=eval(exp)
    ans=eval(input(str(i)+": "+exp+" : "))
    if d == ans:
        score += 1
        print("v")
    else:
        print("x")
        errors.append(i)

print("1: score = ",score)
for i in errors:
    exp=questions[i]
    d=eval(exp)
    ans=eval(input(str(i)+": "+exp+" : "))
    if d == ans:
        score += 1
        print("v")
    else:
        print("x")
if len(errors)>0:
    print("2:score = ",score)