while True:
pm = input("請輸入壹個數字,輸入exit退出程序")
if pm == 'exit':
print('程序已退出')
break
if pm.isdigit(): ?# 判斷輸入的字符串是不是數字
pm = int(pm) ?# 字符串轉化為數字
if 0 <= pm <= 35:
print("優")
elif 35 < pm <= 75:
print("良")
elif 75 < pm <= 115:
print("輕度汙染")
elif 115 < pm <= 150:
print("中度汙染")
elif 150 < pm <= 250:
print("重度汙染")
elif 250 < pm <= 500:
print("嚴重汙染")
else:
print("輸入有誤")
else:
print('輸入有誤')