【学Python自动化】 3. Python 速览学习笔记 (Windows 环境)

weixin_43219667

427人浏览 · 2025-08-31 01:00:00

weixin_43219667 · 2025-08-31 01:00:00 发布

一、Python 用作计算器

1 数字运算

基础算术运算


>>> 2 + 2
4

>>> 50 - 5*6
20

>>> (50 - 5*6) / 4
5.0

>>> 8 / 5  # 除法总是返回浮点数
1.6

整数除法和取余


>>> 17 / 3   # 经典除法
5.666666666666667

>>> 17 // 3  # 向下取整除法
5

>>> 17 % 3   # 取余数
2

>>> 5 * 3 + 2  # 验证公式
17

乘方运算


>>> 5 ** 2  # 5的平方
25

>>> 2 ** 7  # 2的7次方
128

变量赋值和使用


>>> width = 20
>>> height = 5 * 9
>>> width * height
900

>>> n  # 访问未定义变量会报错
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'n' is not defined

混合运算和特殊变量 _


>>> 4 * 3.75 - 1  # 整数会自动转为浮点数
14.0

>>> tax = 12.5 / 100
>>> price = 100.50
>>> price * tax
12.5625

>>> price + _  # _ 表示上一个计算结果
113.0625

>>> round(_, 2)  # 四舍五入到2位小数
113.06

2 文本（字符串）操作

字符串定义


>>> 'spam eggs'  # 单引号
'spam eggs'

>>> "Paris rabbit got your back :)! Yay!"  # 双引号
'Paris rabbit got your back :)! Yay!'

>>> '1975'  # 数字字符串
'1975'

转义字符和原始字符串


>>> 'doesn\'t'  # 转义单引号
"doesn't"

>>> "doesn't"    # 或用双引号
"doesn't"

>>> print('C:\some\name')  # \n 被解释为换行
C:\some
ame

>>> print(r'C:\some\name')  # 原始字符串
C:\some\name

多行字符串


>>> print("""\
Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to
""")

字符串拼接和重复


>>> 3 * 'un' + 'ium'  # 重复+拼接
'unununium'

>>> 'Py' 'thon'  # 相邻字面值自动合并
'Python'

>>> prefix = 'Py'
>>> prefix + 'thon'  # 变量拼接要用 +
'Python'

字符串索引和切片


>>> word = 'Python'
>>> word[0]  # 第一个字符
'P'

>>> word[5]  # 第六个字符
'n'

>>> word[-1]  # 最后一个字符
'n'

>>> word[0:2]  # 切片：0到2（不含2）
'Py'

>>> word[:2]   # 从开始到2
'Py'

>>> word[4:]   # 从4到结束
'on'

>>> word[-2:]  # 最后两个字符
'on'

字符串不可变性


>>> word[0] = 'J'  # 错误：字符串不可修改
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment

>>> 'J' + word[1:]  # 正确：创建新字符串
'Jython'

字符串长度


>>> s = 'supercalifragilisticexpialidocious'
>>> len(s)
34

3 列表操作

列表创建和访问


>>> squares = [1, 4, 9, 16, 25]
>>> squares
[1, 4, 9, 16, 25]

>>> squares[0]  # 索引访问
1

>>> squares[-1]  # 最后一个元素
25

>>> squares[-3:]  # 切片返回新列表
[9, 16, 25]

列表修改


>>> cubes = [1, 8, 27, 65, 125]
>>> cubes[3] = 64  # 修改元素
>>> cubes
[1, 8, 27, 64, 125]

>>> cubes.append(216)  # 添加元素
>>> cubes.append(7 ** 3)
>>> cubes
[1, 8, 27, 64, 125, 216, 343]

列表引用和拷贝


>>> rgb = ["Red", "Green", "Blue"]
>>> rgba = rgb  # 引用同一个对象
>>> rgba.append("Alph")
>>> rgb  # 两个变量都受影响
["Red", "Green", "Blue", "Alph"]

>>> correct_rgba = rgba[:]  # 创建浅拷贝
>>> correct_rgba[-1] = "Alpha"
>>> correct_rgba
["Red", "Green", "Blue", "Alpha"]
>>> rgba  # 原列表不变
["Red", "Green", "Blue", "Alph"]

列表切片赋值


>>> letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> letters[2:5] = ['C', 'D', 'E']  # 替换切片
>>> letters
['a', 'b', 'C', 'D', 'E', 'f', 'g']

>>> letters[2:5] = []  # 删除切片
>>> letters
['a', 'b', 'f', 'g']

>>> letters[:] = []  # 清空列表
>>> letters
[]

列表长度和嵌套列表


>>> letters = ['a', 'b', 'c', 'd']
>>> len(letters)
4

>>> a = ['a', 'b', 'c']
>>> n = [1, 2, 3]
>>> x = [a, n]  # 嵌套列表
>>> x
[['a', 'b', 'c'], [1, 2, 3]]
>>> x[0][1]  # 访问嵌套元素
'b'

二、走向编程的第一步

斐波那契数列示例


# 斐波那契数列：前两项之和等于下一项
a, b = 0, 1  # 多重赋值

while a < 10:
    print(a)
    a, b = b, a + b  # 同时更新两个变量

输出：

print函数的高级用法


>>> i = 256*256
>>> print('The value of i is', i)  # 多个参数
The value of i is 65536

>>> a, b = 0, 1
>>> while a < 1000:
...     print(a, end=',')  # 取消换行，用逗号结尾
...     a, b = b, a+b
...
0,1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,