用Python编程,根据下表标准,输入PM2.5值,输出对应等级,输入-1结束
PM=0
while(PM !=-1):
PM = eval(input("请输入PM2.5数值:"))
if 0<=PM< 50:
print("1级")
if 51<=PM<100:
print("2级")
if 101<=PM<150:
print("3级")
if 151<=PM<200:
print("4级")
if 201<=PM<300:
print("5级")
if PM>300:
print("6级")