python学习笔记

#!/usr/bin/env python3
print(‘hello, world‘)

$ chmod a+x hello.py

# print()会依次打印每个字符串，遇到逗号“,”会输出一个空格
>>> print(‘a‘,‘b‘,‘c‘)
a b c

>>> print(‘a‘)
>>> print(‘b‘)
a
b

>>> name = input(‘input your name:‘)
input your name:lizhixin
>>> name
‘lizhixin‘

>>> r‘\n\r\t‘
‘\\n\\r\\t‘

>>> a = 3
>>> b = a
>>> a = 4
>>> b
3

# 计算机只会处理数字,任何文本最终都会被转化为数字来进入cpu参与运算
# 8 bit(比特) = 1 byte(字节)
# 国际编码Unicode, 转化为‘可变长编码‘ UTF-8, 内存中使用Unicode, 要传输和存储到硬盘就要保存为UTF-8

>>> ord(‘l‘)
108
>>> ord(‘#‘)
35
>>> chr(123)
‘{‘
>>> chr(20013)
‘中‘

# Python的字符串类型是str，在内存中以Unicode表示，一个字符对应若干个字节。如果要在网络上传输，或者保存到磁盘上，就需要把str变为以字节为单位的bytes。

>>> ‘lizhixin‘.encode(‘ascii‘)
b‘lizhixin‘
>>> ‘李治鑫‘.encode(‘utf-8‘)
b‘\xe6\x9d\x8e\xe6\xb2\xbb\xe9\x91\xab‘

>>> b‘grge‘.decode(‘ascii‘)
‘grge‘
>>> b‘\xe6\x9d\x8e\xe6\xb2\xbb\xe9\x91\xab‘.decode(‘utf-8‘)
‘李治鑫‘

>>> ‘Hi, %s, you have $%d.‘ % (‘lizhixin‘, 10000000)
‘Hi, lizhixin, you have $10000000.‘

# 列表 list
>>> a = [1, 2, 3]
>>> a
[1, 2, 3]
# 元组 tuple
>>> b = 1, 2, 3
>>> b
(1, 2, 3)
# 字典 dict
>>> c = {1:2, 3:4, 5:6}
>>> c
{1: 2, 3: 4, 5: 6}
# 集合 set
>>> d = {1, 2, 3, 4}
>>> d
{1, 2, 3, 4}

>>> a = [1, 3, 5, 7, 9]
>>> for num in a:
    print(num)

    
1
3
5
7
9

>>> n = 0
>>> while n <= 10:
    print (n)
    n = n + 1

    
0
1
2
3
4
5
6
7
8
9
10

# 很难一次写对, { }, [], ‘ ‘, 一个都不能错
>>> names = {‘Micheal‘:95, ‘Bob‘:59, ‘Tracy‘:85}
>>> names[‘Micheal‘]
95