Python的psycopg2库怎么使用？

pip install psycopg2

import psycopg2

# 连接到数据库
conn = psycopg2.connect(
    dbname="your_dbname",
    user="your_username",
    password="your_password",
    host="your_host",
    port="your_port"
)

# 创建一个游标对象
cur = conn.cursor()

# 执行SQL查询
cur.execute("SELECT * FROM your_table")

# 获取查询结果
rows = cur.fetchall()

# 关闭游标和连接
cur.close()
conn.close()

from psycopg2 import pool

# 创建一个连接池
conn_pool = pool.ThreadedConnectionPool(
    1,  # 最小连接数
    20,  # 最大连接数
    dbname="your_dbname",
    user="your_username",
    password="your_password",
    host="your_host",
    port="your_port"
)

# 从连接池中获取连接
conn = conn_pool.getconn()

try:
    # 创建游标并执行查询
    cur = conn.cursor()
    cur.execute("SELECT * FROM your_table")
    rows = cur.fetchall()
finally:
    # 返回连接到池中
    conn_pool.putconn(conn)

from psycopg2 import sql

# 批量执行SQL语句
cur = conn.cursor()
records = [('Alice', 25), ('Bob', 30), ('Charlie', 35)]
cur.executemany("INSERT INTO users (name, age) VALUES (%s, %s)", records)
conn.commit()

# 使用copy_from进行大规模数据导入
import csv
from io import StringIO

# 假设有一个CSV文件
with open('users.csv', 'r') as f:
    data = StringIO(f.read())

cur.copy_from(data, 'users', sep=',')
conn.commit()

from psycopg2 import sql

# 安全地构建SQL查询
username = 'Alice'
cur.execute(sql.SQL("SELECT * FROM users WHERE name = {}").format(sql.Literal(username)))