学习python的第二天

注释和“#”号

在学习一门编程语言的时候，最重要的事一定少不了看程序里的注释。一般情况注释有两个功能：第一，可以通过自然语言的方式告诉你某段代码的作用；第二，在运行程序的时候想要禁用某些代码，可以先用注释将代码临时禁用。

练习部分

# A comment, this is so you can read your program later.# Anything after the # is ignored by python.print "I could have code like this. "# and the comment after is ignored#you can also use a comment to "disable" or comment out a piece of code:#print "This won't run."print "This will run."

数字和数学计算

在这章中，我们将接触数学运算符号：

• + 加号
• - 减号
• / 斜杠
• * 星号
• % 百分号
• < 小于号
• > 大于号
• <= 小于等于号
• >= 大于等于号

以上的符号都是用来做运算的，通过练习可以学习这些符号的作用。

练习部分

print "I will now count my chickens:"print "Hens",25 + 30 /6print "Roosters", 100 - 25 * 3 % 4print "How I will count the eggs:"print 3 + 2 + 1 - 5 + 4 % 2 - 1 / 4 + 6print "Is it true that 3 + 2 < 5 - 7 ?"print 3 + 2 < 5 - 7print "What is 3 + 2 ?",3 + 2print "What is 5 - 7 ?",5 - 7print "Oh,that's why it's False."print "How about some more."print "Is it greater ?",5 > -2print "Is it greater or equal ?",5 >= -2print "Is it less or equal ?",5 <= -2

加分习题：

1.用#在每句代码前写一个注释，说明作用

2.使用浮点数重新写一遍ex3.py

# 输出 I will now count my chickens:print "I will now count my chickens:"# 计算 Hensprint "Hens",25.0 + 30 /6# 计算 Roostersprint "Roosters", 100.0 - 25 * 3 % 4# 输出 How I will count the eggs:print "How I will count the eggs:"# 计算 eggsprint 3.0 + 2 + 1 - 5 + 4 % 2 - 1 / 4 + 6# 输出 Is it true that 3 + 2 < 5 - 7 ?print "Is it true that 3 + 2 < 5 - 7 ?"# 判断 3 + 2 和 5 - 7 的关系，输出结果print 3.0 + 2 < 5 - 7# 计算 3 + 2print "What is 3 + 2 ?",3.0 + 2# 计算 5 - 7print "What is 5 - 7 ?",5.0 - 7# 输出 Oh,that's why it's False.print "Oh,that's why it's False."# 输出 How about some more.print "How about some more."# 进行判断print "Is it greater ?",5 > -2print "Is it greater or equal ?",5 >= -2print "Is it less or equal ?",5 <= -2