83 lines
1.2 KiB
Markdown
83 lines
1.2 KiB
Markdown
# 第4章 函数与模块
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## 4.1 函数定义
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```python
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def greet(name):
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"""函数的文档字符串"""
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return f"你好，{name}！"
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msg = greet("张三")
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print(msg) # 你好，张三！
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```
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### 参数类型
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```python
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# 默认参数
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def power(base, exponent=2):
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return base ** exponent
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print(power(3)) # 9
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print(power(2, 3)) # 8
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# 可变参数
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def total(*numbers):
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result = 0
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for n in numbers:
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result += n
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return result
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```
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---
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## 4.2 变量作用域
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```python
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count = 0
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def increment():
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global count
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count += 1
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increment()
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print(count) # 1
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```
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---
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## 4.3 匿名函数
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```python
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square = lambda x: x ** 2
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print(square(5)) # 25
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```
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---
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## 4.4 模块导入
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```python
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import math
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print(math.pi)
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import random
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print(random.randint(1, 100))
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```
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### 常用标准库
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| 模块 | 用途 |
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|------|------|
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| `os` | 操作系统接口 |
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| `json` | JSON处理 |
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| `datetime` | 日期时间 |
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| `random` | 随机数 |
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---
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## 本章练习
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1. 编写一个函数，计算列表中所有元素的平均值
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2. 编写一个函数，统计字符串中每个字符出现的次数
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3. 编写一个模块，包含计算圆面积、矩形面积的函数 |