Python 环境搭建与基础语法

搭好环境，写出第一行代码——Python 之旅从此开始。

Python 生态架构

安装与环境配置

"""
Python 环境搭建
"""
INSTALL_GUIDE = {
"Windows": [
"1. 访问 python.org 下载 3.12+",
"2. 安装时勾选 'Add Python to PATH'",
"3. 终端验证: python --version",
],
"macOS": [
"1. brew install python@3.12",
"2. 或下载官方安装包",
"3. 终端验证: python3 --version",
],
"Linux": [
"1. sudo apt update && sudo apt install python3.12",
"2. sudo apt install python3-pip python3-venv",
"3. 终端验证: python3 --version",
],
}
VENV_COMMANDS = """
# 创建虚拟环境
python -m venv .venv
# 激活（Windows）
.venv\\Scripts\\activate
# 激活（macOS/Linux）
source .venv/bin/activate
# 安装包
pip install requests pandas fastapi
# 导出依赖
pip freeze > requirements.txt
# 从文件安装
pip install -r requirements.txt
"""
IDE_RECOMMENDATIONS = {
"VS Code": "免费，插件丰富，推荐 Python 扩展",
"PyCharm": "专业 IDE，社区版免费",
"Jupyter Notebook": "数据分析利器，交互式编程",
}
for platform, steps in INSTALL_GUIDE.items():
print(f"\n{platform}:")
for step in steps:
print(f"  {step}")

基础语法速览

"""
Python 基础语法
"""
# === 变量与类型 ===
name: str = "Python"          # 字符串
version: float = 3.12         # 浮点数
is_awesome: bool = True       # 布尔值
count: int = 42               # 整数
nothing = None                # 空值
# 类型检查
print(type(name))       # <class 'str'>
print(isinstance(name, str))  # True
# === 字符串操作 ===
greeting = f"Hello, {name} {version}!"  # f-string 格式化
multiline = """
这是多行
字符串
"""
print(greeting.upper())        # 转大写
print("python" in greeting.lower())  # True，包含检查
# === 基本运算 ===
print(10 / 3)    # 3.333... 浮点除
print(10 // 3)   # 3       整除
print(10 % 3)    # 1       取余
print(2 ** 10)   # 1024    幂运算
# === 比较与逻辑 ===
x = 10
print(1 < x < 100)           # True，链式比较
print(x == 10 and x > 5)     # True
print(x == 0 or x == 10)     # True
print(not False)              # True

控制流

"""
条件判断与循环
"""
# === if-elif-else ===
score = 85
if score >= 90:
grade = "A"
elif score >= 80:
grade = "B"
elif score >= 70:
grade = "C"
else:
grade = "D"
print(f"成绩 {score} 分，等级 {grade}")
# 三元表达式
result = "及格" if score >= 60 else "不及格"
# === match-case (Python 3.10+) ===
command = "start"
match command:
case "start":
print("启动")
case "stop":
print("停止")
case "restart":
print("重启")
case _:
print("未知命令")
# === for 循环 ===
fruits = ["苹果", "香蕉", "橙子"]
# 基本遍历
for fruit in fruits:
print(fruit)
# 带索引遍历
for i, fruit in enumerate(fruits):
print(f"{i}: {fruit}")
# range
for i in range(5):       # 0, 1, 2, 3, 4
print(i, end=" ")
for i in range(1, 10, 2):  # 1, 3, 5, 7, 9
print(i, end=" ")
# === while 循环 ===
n = 1
while n <= 5:
print(n, end=" ")
n += 1
# === 循环控制 ===
for i in range(10):
if i == 3:
continue     # 跳过 3
if i == 7:
break        # 到 7 停止
print(i, end=" ")  # 输出: 0 1 2 4 5 6

函数基础

"""
函数定义与使用
"""
# === 基本函数 ===
def greet(name: str) -> str:
"""向用户问候"""
return f"你好, {name}!"
print(greet("Python"))
# === 默认参数 ===
def power(base: int, exp: int = 2) -> int:
"""计算幂"""
return base ** exp
print(power(3))      # 9
print(power(2, 10))  # 1024
# === 可变参数 ===
def total(*args: int) -> int:
"""求和"""
return sum(args)
print(total(1, 2, 3, 4, 5))  # 15
# === 关键字参数 ===
def create_user(**kwargs) -> dict:
"""创建用户"""
return kwargs
user = create_user(name="张三", age=25, role="developer")
print(user)  # {'name': '张三', 'age': 25, 'role': 'developer'}
# === 多返回值 ===
def divmod_custom(a: int, b: int) -> tuple[int, int]:
"""返回商和余数"""
return a // b, a % b
quotient, remainder = divmod_custom(17, 5)
print(f"17 ÷ 5 = {quotient} 余 {remainder}")
# === 类型提示 (Python 3.12) ===
type Vector = list[float]
def dot_product(a: Vector, b: Vector) -> float:
"""向量点积"""
return sum(x * y for x, y in zip(a, b))
print(dot_product([1, 2, 3], [4, 5, 6]))  # 32

模块与包

"""
模块导入与组织
"""
# === 导入方式 ===
import os                        # 导入整个模块
from pathlib import Path         # 导入特定类
from datetime import datetime as dt  # 别名导入
import json, csv                 # 多模块导入
# === 常用标准库 ===
USEFUL_STDLIB = {
"os / sys": "系统操作、环境变量",
"pathlib": "现代路径操作（推荐替代 os.path）",
"json": "JSON 读写",
"datetime": "日期时间处理",
"collections": "高级数据结构 (Counter, defaultdict)",
"itertools": "迭代器工具",
"functools": "函数工具 (lru_cache, partial)",
"typing": "类型注解",
"dataclasses": "数据类",
"re": "正则表达式",
"logging": "日志系统",
"unittest / pytest": "测试框架",
}
# === 创建自己的包 ===
PACKAGE_STRUCTURE = """
my_package/
├── __init__.py      # 包标识（可以为空）
├── core.py          # 核心逻辑
├── utils.py         # 工具函数
└── models/
├── __init__.py
└── user.py
# 使用
from my_package.core import main_function
from my_package.models.user import User
"""
for module, desc in USEFUL_STDLIB.items():
print(f"  {module}: {desc}")

本章小结

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