python 笔记 if语句的简单使用 《笨办法学Python》习题29 ——1.2

习题 29:  如果(if)目标与感悟：
•if语句的简单应用
•增值符 x += 1
 
ex29.py
#-*-coding:utf-8-*-
#本章涉及内容十分简单，即if sentence1: sentence2,
#if语句用法和函数有点像，第二行都需要缩进4个字符
 
#if语句执行过程如下：
#先执行语句一即判断语句，如果判断语句为真，则执行语句二。
#此处不一定是语句，只是一个条件，其值也可以是布尔值
 
 
peolple = 20
cats = 30
dogs = 15
 
if peolple < cats:
print"Too many cats! The world is doomed!"
if peolple > cats:
print"Not many cats! The world is saved!"
 
if peolple < dogs:
print"The world is drooled on!"
if peolple > dogs:
print"The world is dry!"
#此处出现新的符号+=,作者命名为加值符，其等同与：
#x += 1 和 x = x + 1
#其更简洁，此处dogs += 5,dogs = 20
dogs += 5
 
 
#下面3个条件都成立，所以全部输出
if peolple >= dogs:
print"People are greater than or equal to dogs."
if peolple <= dogs:
print"People are less than or equal to dogs."
if peolple == dogs:
print"People are dogs."
 
print "\t \t boolean test!"
print "\t -------------------------------- "
a = "test"
b = "testing"
if a != b:
print "\t \t Is true!"
print "\t\tboolean can be used"
print "\t -------------------------------- "


运行结果: