# Python 学习笔记

Python 是一门优雅且强大的编程语言。

## 基本语法

```python
# 列表推导式
squares = [x**2 for x in range(10)]
print(squares)  # [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

# 字典推导式
word_lengths = {word: len(word) for word in ['hello', 'world', 'python']}
print(word_lengths)
```

## 装饰器

```python
def timer(func):
    def wrapper(*args, **kwargs):
        import time
        start = time.time()
        result = func(*args, **kwargs)
        print(f"{func.__name__} took {time.time() - start:.4f}s")
        return result
    return wrapper

@timer
def slow_function():
    import time
    time.sleep(1)
    return "Done"

print(slow_function())
```

## 常用库

1. **NumPy** - 科学计算
2. **Pandas** - 数据分析
3. **Flask** - Web 框架
4. **Requests** - HTTP 请求