CPU 相当于人的大脑
内存 存储数据 4G 8G 16G 32G --成本高 断电即消失
硬盘 1T 固态硬盘 机械硬盘 应该长久保存的数据
重要文件
操作系统
应用程序
python2 源码不标准,混乱,重复代码太多
python3 统一 标准,去除重复代码
优点
缺点
优点:运行速度快
缺点:开发效率低,不能跨平台
举例:C C++
优点:开发效率高,可以跨平台
缺点:运行速度慢
举例:Python Php
python2的默认编码方式是ascii码 (解决方法: 首行 #-*- encoding:utf-8 -*-)
python3的默认编码方式是utf-8码
转换为C语言能识别的字节码
一次性全部编译成字节码
转换为Java语言能识别的字节码
a = 1
b = 2
c = a + b
d = a - b
BIRTH_OF_CHINA = 1949
PI = 3.14
#单行注释
'''
多行注释
多行注释
多行注释
'''
"""
多行注释
多行注释
多行注释
"""
name = input('请输入姓名')
age = input('请输入年龄')
print('你好,' + name)
print('你今年' + age + '岁')
12.3 456
+ - * / **(幂次) %(取余)
a = 1 + 2
b = a + 3
c = 2 ** 4
d = 15 % 2
'hello world' '你好'
Python中凡是用引号引起来的都是字符串
可相加:字符串拼接
可相乘:str * int
a = 'hello python'
b = 'my name is WJZ'
print(a + b)
print(a * 3)
True False
type()
a = 111
b = 'hello python'
c = True
print(type(a))
print(type(b))
print(type(c))
1 count = 1
2 flag = True
3 while flag:
4 print(count)
5 count += 1
6 if count > 100:
7 flag = False
8 print('------------------------------------------')
9 count = 1
10 sum = 0
11 while count <= 100:
12 print(count)
13 sum = sum + count
14 count += 1
15 print(sum)
16 print('------------------------------------------')
17 print('111')
18 while True:
19 print('222')
20 print('333')
21 break
22 print('444')
23 print('abc')
24 print('------------------------------------------')
25 count = 1
26 while True:
27 print(count)
28 count += 1
29 if count > 100:
30 break
31 print('------------------------------------------')
32 count = 0
33 while count <= 100:
34 count += 1
35 if count >5 and count < 95:
36 continue
37 print('loop', count)
38 print('---out of while loop---')
无限循环
终止循环:改变条件,使其不成立
break(终止循环)
continue(结束本次循环)
1 count = 1
2 flag = True
3 while flag:
4 print(count)
5 count += 1
6 if count > 100:
7 flag = False
8 print('------------------------------------------')
9 count = 1
10 sum = 0
11 while count <= 100:
12 print(count)
13 sum = sum + count
14 count += 1
15 print(sum)
16 print('------------------------------------------')
17 print('111')
18 while True:
19 print('222')
20 print('333')
21 break
22 print('444')
23 print('abc')
24 print('------------------------------------------')
25 count = 1
26 while True:
27 print(count)
28 count += 1
29 if count > 100:
30 break
31 print('------------------------------------------')
32 count = 0
33 while count <= 100:
34 count += 1
35 if count >5 and count < 95:
36 continue
37 print('loop', count)
38 print('---out of while loop---')