笨办法29IF语句

 people = 20
 cats = 30
 dogs = 15

 if people < cats:
     print "Too many cats! The world is doomed!"

 if people > cats:
     print "Not many cats! The world is saved!"

 if people < dogs:
     print "The world is drooled on!"

 if people > dogs:
     print "The world is dry!"

 dogs += 5

 if people >= dogs:
     print "People are greater than or equal to dogs."

 if people <=dogs:
     print "People are less than or equal to dogs."

 if people == dogs:
     print "people are dogs."

dogs += 5 即 dogs = dogs + 5

此时dogs=20，同时满足三个条件，输出三句