Ex29 What If

条件语句

从 Ex28 介绍Boolean类型，紧接着，在本练习，用代码感受一翻。Zed 的书过半，才开始引入条件语句，确实有讲究。大概对于初学者来说，逻辑语句，不太容易接受，看看“三段论”在人群中的普及就知道大概了。示例代码 Ex29:

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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."

运行结果如图:

小结

强制缩进是python的特色，有人可能认为这样呆板，但是对于多数新手来说，这道紧箍咒确实能训练良好的书写风格。