Writing to MySQL database with pandas using SQLAlchemy, to_sql

问题

trying to write pandas dataframe to MySQL table using to_sql. Previously been using flavor=\'mysql\', however it will be depreciated in the future and wanted to start the transition to using SQLAlchemy engine.

sample code:

import pandas as pd
import mysql.connector
from sqlalchemy import create_engine

engine = create_engine(\'mysql+mysqlconnector://[user]:[pass]@[host]:[port]/[schema]\', echo=False)
cnx = engine.raw_connection()
data = pd.read_sql(\'SELECT * FROM sample_table\', cnx)
data.to_sql(name=\'sample_table2\', con=cnx, if_exists = \'append\', index=False)

The read works fine but the to_sql has an error:

DatabaseError: Execution failed on sql \'SELECT name FROM sqlite_master WHERE type=\'table\' AND name=?;\': Wrong number of arguments during string formatting

Why does it look like it is trying to use sqlite? What is the correct use of a sqlalchemy connection with mysql and specifically mysql.connector?

I also tried passing the engine in as the connection as well, and that gave me an error referencing no cursor object.

data.to_sql(name=\'sample_table2\', con=engine, if_exists = \'append\', index=False)
>>AttributeError: \'Engine\' object has no attribute \'cursor\'

回答1:

Using the engine in place of the raw_connection() worked:

import pandas as pd
import mysql.connector
from sqlalchemy import create_engine

engine = create_engine('mysql+mysqlconnector://[user]:[pass]@[host]:[port]/[schema]', echo=False)
data.to_sql(name='sample_table2', con=engine, if_exists = 'append', index=False)

Not clear on why when I tried this yesterday it gave me the earlier error.

回答2:

Alternatively, use pymysql package...

import pymysql
from sqlalchemy import create_engine
cnx = create_engine('mysql+pymysql://[user]:[pass]@[host]:[port]/[schema]', echo=False)

data = pd.read_sql('SELECT * FROM sample_table', cnx)
data.to_sql(name='sample_table2', con=cnx, if_exists = 'append', index=False)

回答3:

Using pymysql and sqlalchemy, this works for Pandas v0.22:

import pandas as pd
import pymysql
from sqlalchemy import create_engine

user = 'yourUserName'
passw = 'password'
host =  'hostName'  # either localhost or ip e.g. '172.17.0.2' or hostname address 
port = 3306 
database = 'dataBaseName'

mydb = create_engine('mysql+pymysql://' + user + ':' + passw + '@' + host + ':' + str(port) + '/' + database , echo=False)

directory = r'directoryLocation'  # path of csv file
csvFileName = 'something.csv'

df = pd.read_csv(os.path.join(directory, csvFileName ))

df.to_sql(name=csvFileName[:-4], con=mydb, if_exists = 'replace', index=False)

"""
if_exists: {'fail', 'replace', 'append'}, default 'fail'
     fail: If table exists, do nothing.
     replace: If table exists, drop it, recreate it, and insert data.
     append: If table exists, insert data. Create if does not exist.
"""

回答4:

I know in the title of the question is included the word SQLAlchemy, however I see in the questions and answers the need to import pymysql or mysql.connector, and also is possible to do the job with pymysql, withouth calling SQLAlchemy.

import pymysql
user = 'root'
passw = 'my-secret-pw-for-mysql-12ud' # In previous posts variable "pass"
host =  '172.17.0.2'
port = 3306

database = 'sample_table' # In previous posts similar to "schema"

conn = pymysql.connect(host=host,
                       port=port,
                       user=user, 
                       passwd=passw,  
                       db=database)

data.to_sql(name=database, con=conn, if_exists = 'append', index=False, flavor = 'mysql')

I think this solution could be good althought it is not using SQLAlchemy.

来源：https://stackoverflow.com/questions/30631325/writing-to-mysql-database-with-pandas-using-sqlalchemy-to-sql

标签

python

mysql

pandas

sqlalchemy

mysql-connector