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今日内容
变量
定义:将程序运行中的中间值临时存储起来,以便再次使用
变量一般用于后期开发使用
-
变量名使用规范:
数字、字母、下划线组成
不能以数字开头
-
禁止使用python关键字
['False', 'None', 'True', 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']
变量名要具有可描述性
变量名要区分大小写
变量名不能使用拼音和中文
-
推荐写法
7.1驼峰体
Alexdfkasd = "adsdf"
7.2下划线
alex_name = "asdfasdf"
常量及注释
常量
定义:变量名大写就是常量
注意:其他语言中常量不能被修改,python中的常量可以被修改,但是一般不要修改
常量一般用于文件配置
注释
定义:给一些晦涩难懂的代码进行注释
单行注释:# 注释后的代码不会被执行,且不占内存
多行注释:''' '''或”“” “”“可以换行
PEP8开发规范:代码不宜过长,超过界面分界线
基础数据类型
int整型
- 用于计算和比较:+、-、*、/、
str字符串
“ ”
‘ ’
“‘ ”’
bool布尔值
True False
str(int)时字符串内容只能是数字
python2和python3的区别
-
python2
- 源码不统一
- 代码有重复
- print不用加括号
- 做除法时,输出为整数
- raw_input获取到全为字符串,input获取到什么类型,输出就是什么类型
-
python3
- 代码统一
- 代码没有重复
- print要加括号
- 做除法时,输出是浮点型
- input获取到的全为字符串
流程控制语句
-
if嵌套
-
如果 条件:
缩进 结果
缩进 如果 条件:
缩进 结果
用于判断
-
-
if else 二选一
如果 条件:
-
缩进 结果
否则:
缩进 结果
-
if elif elif elif 多选一或零
-
如果 条件:
缩进 结果
在如果 条件:
缩进 结果
在如果 条件:
缩进 结果
-