Python 3.7.x 介绍-1概述

Posted 2022-12-12 「已注销」

1 容易学习
高效的高级数据结构
面向对象编程的简单方法
简洁的语法和动态类型

Python解释器
通过C / C ++轻松扩展
来自主要Python平台的大量源代码或二进制文件库

使用Python解释器
通常安装在c：\\ python37 Python命令行示例：。
python -c命令[arg] …
python -m module [arg] …参数传递。
通过import sys访问参数列表。

互动模式。
从tty读取命令时，解释器将处于交互模式。在此模式下，它使用>>>来提示下一个命令。

Python源文件被视为UTF-8，因此所有大多数语言字符都可以存储在字符串中。
标准的lib使用ASCII

简单Python实例
1 计算器

>>> 2 + 2
4
>>> 50 - 5*6
20
>>> (50 - 5*6) / 4
5.0
>>> 8 / 5  # division always returns a floating point number
1.6
>>> 5 ** 2  # 5 squared
25
>>> 2 ** 7  # 2 to the power of 7
128
>>> width = 20
>>> height = 5 * 9
>>> width * height
900

2 字符串

>>> '"Isn\\'t," they said.'
'"Isn\\'t," they said.'
>>> print('"Isn\\'t," they said.')
"Isn't," they said.
>>> s = 'First line.\\nSecond line.'  # \\n means newline
>>> s  # without print(), \\n is included in the output
'First line.\\nSecond line.'
>>> print(s)  # with print(), \\n produces a new line
First line.
Second line.
>>> # 3 times 'un', followed by 'ium'
>>> 3 * 'un' + 'ium'
'unununium'
>>> word = 'Python'
>>> word[0]  # character in position 0
'P'
>>> word[5]  # character in position 5
'n'
>>> word[-1]  # last character
'n'
>>> word[-2]  # second-last character
'o'
>>> word[-6]
'P'
 +---+---+---+---+---+---+
 | P | y | t | h | o | n |
 +---+---+---+---+---+---+
 0   1   2   3   4   5   6
-6  -5  -4  -3  -2  -1

3 列表

>>> squares = [1, 4, 9, 16, 25]
>>> squares
[1, 4, 9, 16, 25]
>>> squares[0]  # indexing returns the item
1
>>> squares[-1]
25
>>> squares[-3:]  # slicing returns a new list
[9, 16, 25]
>>> squares + [36, 49, 64, 81, 100]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]