Python编程从入门到实践自学/第二章

变量值可随时修改，Python始终记录变量最新值

变量名只能包含字母、数字和下划线，不能包含空格，但能使用下划线来分隔单词，变量名不能以数字打头

慎用小写字母l和大写字母O防止被错看为数字1和0

变量是可以赋给值的标签，也可以说是变量指向特定的值

变量后面的.是让Python对该变量执行指定操作的意思

title（）是让每个单词首字母大写的方法

upper（）是让每个单词所有字母大写的方法

lower（）是让每个单词所有字母小写的方法

字符串中插入变量的值，可在前引号前加上字母f，再将要插入的变量放在花括号内

制表符\t

换行符\n

rstrip（）是删除末尾空白的方法

lstrip（）是删除开头空白的方法

strip（）是删除两边空白的方法

可用下划线给很大的数分组，比如14000000000可以写成14_000_000_000而Python打印这种数不会打印其中的下划线

将特定的变量视为常量可将其字母全部大写

#用来注释

Python之禅

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!