Python pymysql 有效，但 sqlalchemy 无效

Question

I'm on an EC2 instance Centos7. Using Python 3.9.10. Virtualenv activated with following libraries sqlalchemy , pandas , pymysql installed.

So this works fine:

import os
import pymysql
dw = {
    "host": os.environ.get("DW_HOST"),
    "database": os.environ.get("DW_DATABASE"),
    "user": os.environ.get("DW_USER"),
    "password": os.environ.get("DW_PASS"),
}
conn = pymysql.connect(**dw)
with conn.cursor() as cur:
    cur.execute("SELECT * FROM table LIMIT 10")
    data = cur.fetchall()
    for row in data:
        print(row)

This doesn't and I don't know why ( works locally ):

import sqlalchemy
import pandas as pd
import os
dw = {
    "host": os.environ.get("DW_HOST"),
    "database": os.environ.get("DW_DATABASE"),
    "user": os.environ.get("DW_USER"),
    "password": os.environ.get("DW_PASS"),
}
engine = sqlalchemy.create_engine(f'mysql+pymysql://{dw["user"]}:{dw["password"]}@{dw["host"]}/{dw["database"]}')
df = pd.read_sql("SELECT * FROM table LIMIT 10", engine)
df

Getting error:

sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'xyz@cluster-abc.region.rds.amazonaws.com' ([Errno -2] Name or service not known)")
(Background on this error at: https://sqlalche.me/e/14/e3q8)

Also tried:

conn_string = f'mysql+pymysql://{dw["user"]}:{dw["password"]}@{dw["host"]}/{dw["database"]}'
df = pd.read_sql("SELECT * FROM table LIMIT 10", conn_string)

Also tried:

• Adding port number 3306
• Adding .connect() method onto engine

Answer 1

尝试显式传递端口号。