Python编程实战：解决常见编程问题

```python
# 打开文件
with open('example.txt', 'r') as file:
    # 读取文件内容
    content = file.read()
    # 打印文件内容
    print(content)
```

```python
# 定义一个包含数字的列表
numbers = [5, 3, 8, 1, 4]
# 使用sort()方法对列表进行排序
numbers.sort()
# 打印排序后的列表
print(numbers)  # 输出：[1, 3, 4, 5, 8]
```

```python
# 定义一个包含小写字母的字符串
string = "hello world"
# 使用upper()方法将字符串转换为大写字母
upper_string = string.upper()
# 打印转换后的字符串
print(upper_string)  # 输出：HELLO WORLD
```

```python
# 定义函数
def sum_two_numbers(a, b):
    return a + b
# 调用函数并打印结果
result = sum_two_numbers(3, 5)
print(result)  # 输出：8
```

```python
try:
    # 尝试打开不存在的文件
    with open('nonexistent_file.txt', 'r') as file:
        content = file.read()
except FileNotFoundError:
    # 捕获文件不存在异常并打印错误信息
    print("文件不存在，请检查文件名和路径是否正确。")
```

```python
import socket
# 创建TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# 绑定端口
server_address = ('localhost', 12345)
print('Starting up on {} port {}'.format(*server_address))
sock.bind(server_address)
# 监听连接
sock.listen(1)
while True:
    print('Waiting for a connection')
    connection, client_address = sock.accept()
    
    try:
        print('Connection from', client_address)
        # 接收数据
        while True:
            data = connection.recv(1024)
            print('Received {!r}'.format(data))
            if data:
                print('Sending data back to the client')
                connection.sendall(data)
            else:
                print('No more data from', client_address)
                break
    finally:
        # 清理连接
        connection.close()
```

```python
import threading
import time
# 定义一个线程函数
def worker():
    print("Worker thread is starting.")
    time.sleep(2)  # 模拟耗时任务
    print("Worker thread has finished.")
# 创建线程对象
thread = threading.Thread(target=worker)
# 启动线程
thread.start()
# 等待线程执行完毕
thread.join()
print("Main thread continues after the worker thread has finished.")
```

```python
import sqlite3
# 连接SQLite数据库（如果不存在则创建）
conn = sqlite3.connect('example.db')
# 创建一个游标对象
cursor = conn.cursor()
# 执行SQL语句创建表
cursor.execute('''CREATE TABLE IF NOT EXISTS users
                 (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)''')
# 插入数据
cursor.execute("INSERT INTO users (name, age) VALUES (?, ?)", ("Alice", 30))
# 提交事务
conn.commit()
# 查询数据
cursor.execute("SELECT * FROM users")
rows = cursor.fetchall()
for row in rows:
    print(row)
# 关闭游标和连接
cursor.close()
conn.close()
```