python使用read_sql与to_sql读写数据库

文章目录

详细说明
示例程序

详细说明

使用pandas读写数据库的方法（以Mysql为例）如下：

首先是打包一个工具函数：

py 复制代码

import pandas as pd
import numpy as np
from sqlalchemy import create_engine, text


def get_sql_engine():
    # 数据库
    mysql_config = {
        "db": "test_db",
        "host": "127.0.0.1",
        "user": "test_user",
        "password": "test_pass",
        "port": 3306,
    }
    engine = create_engine(
        "mysql+pymysql://{}:{}@{}:{}/{}".format(mysql_config['user'], mysql_config['password'], mysql_config['host'],
                                                mysql_config['port'], mysql_config['db']))
    return engine

读取数据库.read_sql()的方法：

py 复制代码

engine = get_sql_engine()

# ======== 写入 ===========
data_df = pd.DataFrame(np.random.random(size=(100, 5)))
data_df.to_sql('test_data_df', con=engine, if_exists='replace', index=False)

读取数据库read_sql()的方法：
py 复制代码
```
 data_df = pd.read_sql_query(text('select * from test_data_df'), con=engine.connect())
```
在读取的时候容易报错，有几个要点：
1. 首先导入from sqlalchemy import text，然后以text(sql语句)的形式传入第一个参数
2. 在第二个参数需要使用engine.connect()

示例程序

py 复制代码

import pandas as pd
import numpy as np
from sqlalchemy import create_engine, text


def get_sql_engine():
    # 数据库
    mysql_config = {
        "db": "test_db",
        "host": "127.0.0.1",
        "user": "test_user",
        "password": "test_pass",
        "port": 3306,
    }
    engine = create_engine(
        "mysql+pymysql://{}:{}@{}:{}/{}".format(mysql_config['user'], mysql_config['password'], mysql_config['host'],
                                                mysql_config['port'], mysql_config['db']))
    return engine


def main():
    engine = get_sql_engine()
    # ======== 写入 ===========
    data_df = pd.DataFrame(np.random.random(size=(100, 5)))
    data_df.to_sql('test_data_df', con=engine, if_exists='replace', index=False)
    # ======== 读取 ===========
    data_df = pd.read_sql_query(text('select * from test_data_df'), con=engine.connect())


if __name__ == '__main__':
    main()