if单分支，二分支，多分支

# 单分支
guess = input("单分支请输入0或者1:")
if guess=="1":
    print("你当前输入的为1，输入0则不提示")
#二分支 紧凑形式
guess1 = eval(input("请输入99或100:"))
print("猜{}了".format("对" if guess1==99 else "错"))
#多分支结构
guess2 = eval(input("期末考试为:"))
if guess2 >= 90:
    grade ="A"
elif guess2 >= 80:
    frade ="B"
elif guess2 >=70:
    grade= "C"
elif guess2 >=60:
    grade="D"
print("等级为{}".format(grade))