Python3学习笔记

简述

Life is short, you need Python.

Shut up and show me the code.

基础语法

编码

Python 3 源码文件默认以 UTF-8 编码。也可以自行指定。

# -*- coding: <encoding_name> -*-

encoding_name 为 pyhton 支持的有效编码

例如：

# -*- coding: gb2312 -*-

或

# -*- coding: cp-1252 -*-

关键字

import keyword

keyword.kwlist

['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']

注释

# 单行注释

'''
多行
注释
'''

"""
还是
多行
注释
"""

行与缩进

Python最具特色的就是使用缩进来表示代码块。

行缩进使用4个空格，或将tab调整为4个空格。

#!/usr/bin/env python
# -*- coding: utf-8 -*-


class Year(object):

    def __init__(self):
        self.do_better()

    def do_better(self, day=1):
        if day < 365:
            day += 1
            self.do_better(day)

if __name__ == '__main__':
    new_year = Year()

多行语句

game_machines = 'PS4,' + \
                'Xbox,' + \
                'Nintendo Switch'

print(game_machines)

PS4,Xbox,Nintendo Switch

game_machines = ['PS4',
                 'Xbox',
                 'Nintendo Switch']

print(game_machines)

['PS4', 'Xbox', 'Nintendo Switch']

数据类型

内置对象

  1. 数字
  2. 字符串
  3. 列表
  4. 字典
  5. 元组
  6. 集合
  7. 文件
  8. None
  9. 布尔型
  10. ...

数字

# int 整数型
1 + 2

3

# float 浮点型
1.5 * 3

4.5

# float 浮点型
3.14159 * 3

# 浮点计算会存在精度问题需要特别处理
9.424769999999999

字符串

字符串格式化

version >= 3.6

msg = 'world!'
print(f'hello {msg}')

hello world!

d = {'a':1, 'b':3.1415927}
print(f'a = {d["a"]}')
print(f'b = {d["b"]}')
print(f'b = {d["b"]:.2f}')
print(f'a + b = {d["a"] + d["b"]:.2f}')

a = 1
b = 3.1415927
b = 3.14
a + b = 4.14

f'mapping is { {a:b for (a, b) in ((1, 2), (3, 4))} }'

'mapping is {1: 2, 3: 4}'

赋值、浅拷贝、深拷贝

坑过

import copy

a = ["空银子", {"age": 15}]
# 赋值
b = a
# 浅拷贝
c = a.copy()
# 深拷贝
d = copy.deepcopy(a)

print(f'a is {a}, id is {id(a)}')
print('-' * 35)
print(f'b is {b}, id is {id(b)}')
print(f'c is {c}, id is {id(c)}')
print(f'd is {d}, id is {id(d)}\r\n')
print(f'a[1] is {a[1]}, id is {id(a[1])}')
print('-' * 35)
print(f'b[1] is {b[1]}, id is {id(b[1])}')
print(f'c[1] is {c[1]}, id is {id(c[1])}')
print(f'd[1] is {d[1]}, id is {id(d[1])}\r\n')
print('Changed a: a[0] = "雏鹤爱", a[1]["age"] = 9\r\n')
a[0] = "雏鹤爱"
a[1]["age"] = 9
print(f'a is {a}, id is {id(a)}')
print('-' * 35)
print(f'b is {b}, id is {id(b)}')
print(f'c is {c}, id is {id(c)}')
print(f'd is {d}, id is {id(d)}\r\n')
print(f'a[1] is {a[1]}, id is {id(a[1])}')
print('-' * 35)
print(f'b[1] is {b[1]}, id is {id(b[1])}')
print(f'c[1] is {c[1]}, id is {id(c[1])}')
print(f'd[1] is {d[1]}, id is {id(d[1])}')

a is ['空银子', {'age': 15}], id is 4415182472
-----------------------------------
b is ['空银子', {'age': 15}], id is 4415182472
c is ['空银子', {'age': 15}], id is 4415182408
d is ['空银子', {'age': 15}], id is 4415184200

a[1] is {'age': 15}, id is 4413290608
-----------------------------------
b[1] is {'age': 15}, id is 4413290608
c[1] is {'age': 15}, id is 4413290608
d[1] is {'age': 15}, id is 4414213144

Changed a: a[0] = "雏鹤爱", a[1]["age"] = 9

a is ['雏鹤爱', {'age': 9}], id is 4415182472
-----------------------------------
b is ['雏鹤爱', {'age': 9}], id is 4415182472
c is ['空银子', {'age': 9}], id is 4415182408
d is ['空银子', {'age': 15}], id is 4415184200

a[1] is {'age': 9}, id is 4413290608
-----------------------------------
b[1] is {'age': 9}, id is 4413290608
c[1] is {'age': 9}, id is 4413290608
d[1] is {'age': 15}, id is 4414213144

To be continued ...

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