Python中如何连接数据库？

import sqlite3

# 连接到数据库，如果文件不存在会自动创建
conn = sqlite3.connect('example.db')

# 创建一个游标对象，用于执行SQL命令
cursor = conn.cursor()

# 创建表
cursor.execute('''
    CREATE TABLE IF NOT EXISTS users (
        id INTEGER PRIMARY KEY,
        name TEXT NOT NULL,
        email TEXT NOT NULL
    )
''')

# 插入数据
cursor.execute("INSERT INTO users (name, email) VALUES (?, ?)", ('Alice', 'alice@example.com'))

# 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()

import mysql.connector
from mysql.connector import pooling

# 创建连接池
dbconfig = {
    "database": "your_database",
    "user": "your_username",
    "password": "your_password",
    "host": "localhost"
}

connection_pool = mysql.connector.pooling.MySQLConnectionPool(
    pool_name="mypool",
    pool_size=5,
    **dbconfig
)

# 从连接池中获取连接
conn = connection_pool.get_connection()
cursor = conn.cursor()

# 执行操作
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()

import sqlite3

conn = sqlite3.connect('example.db')
cursor = conn.cursor()

try:
    # 开始事务
    cursor.execute('BEGIN')

    # 执行多个操作
    cursor.execute("INSERT INTO users (name, email) VALUES (?, ?)", ('Bob', 'bob@example.com'))
    cursor.execute("INSERT INTO users (name, email) VALUES (?, ?)", ('Charlie', 'charlie@example.com'))

    # 提交事务
    conn.commit()
except sqlite3.Error as e:
    # 如果发生错误，回滚事务
    conn.rollback()
    print(f"An error occurred: {e}")
finally:
    # 关闭游标和连接
    cursor.close()
    conn.close()

import psycopg2

try:
    conn = psycopg2.connect(
        database="your_database",
        user="your_username",
        password="your_password",
        host="localhost",
        port="5432"
    )
    cursor = conn.cursor()

    # 执行操作
    cursor.execute("SELECT * FROM users")
    rows = cursor.fetchall()
    for row in rows:
        print(row)

except psycopg2.Error as e:
    print(f"Database error: {e}")
finally:
    if cursor:
        cursor.close()
    if conn:
        conn.close()