python学习11——if 语句。

people=int(input("How many people are there in this city?"))
cats = int(input("How many cats are there in this city?"))
dogs = int(input("How many dogs are there in this city?"))
if people < cats:
 print("Too many cats! The world is doomed!")
elif people > cats:
 print("Not many cats! The world is saved!")
else:
 print("We can't decide.")
dogs += 10
if people >= dogs:
 print ("People are greater than or equal to dogs.")
else:
 print("People are less than dogs")

输出结果：

注意：

if 、elif、else 后需要加冒号。

数值型数据需要使用int()。

测试小游戏：

print("Now you are lost in the forest, you can see a house in your left and a light comes from right, where do you want to go?")
print("1. To the house in the left.")
print("2. To the light in the right.")
choose_1=input("*")
if choose_1 == "1":
 print("There are some food in the table, will you eat it?")
 print("1. Yes, I\'m so hungry.")
 print("2. No, I will leave tomorrow.")
 choose_2 =input("*")
 if choose_2 =="1":
  print("You ate poison and died, good job!")
 else:
  print("You wake up the other day, and find the way back home.")
elif choose_1=="2":
 print("You find the thing that shines.\n1. You pick it up and hope it can help you find the way.\n2.You throw it away.")
 choose_3=input("*")
 if choose_3=="1":
  print("It was a shining snake and you were biten then die. Good job!")
 elif choose_3=="2":
  print("You were lost in the forest forever.")
 else:
  print("You wake up and it was just a bad dream.")
else:
 print("You stood here until the wolf came and ate you.")