字符串定义出错

""
bmr 基础代谢率计算
"""
def main():
    y_or_n = input('是否退出程序：')
while   y_or_n == 'n':
    # 性别
 gender = input('请输入您的性别:')
    # 体重 (kg)
 weight = float(input('体重:'))
    # 身高 (cm)
 hight = float(input('身高:'))
    # 年龄
 age = int(input ('年龄:'))
if gender == "男":
    bmr = 13.7*weight + 5.0*hight - 6.8*age + 66
elif gender =="女":
    bmr = 9.6*weight + 1.8*hight - 4.7*age + 656
else :
    bmr = -1
if bmr != -1:
     print("基础代谢率 ：",bmr)
else :
    print("暂不支持该性别")
"""gender = "男"
weight = 70
height = 175
age = 24
if gender == "男":
    bmr = 13.7*weight + 5.0*height - 6.8*age + 66
elif gender =="女":
    bmr = 9.6*weight + 1.8*height - 4.7*age + 656
else :
    bmr = -1
    """
y_or_n == intput("是否退出程序(y/n)?:")
if __name__ =="__main__":
    main()
报错 代码 ：    while   y_or_n == 'n':
NameError: name 'y_or_n' is not defined