How to insert pandas dataframe via mysqldb into database?

问题

I can connect to my local mysql database from python, and I can create, select from, and insert individual rows.

My question is: can I directly instruct mysqldb to take an entire dataframe and insert it into an existing table, or do I need to iterate over the rows?

In either case, what would the python script look like for a very simple table with ID and two data columns, and a matching dataframe?

回答1:

Update:

There is now a to_sql method, which is the preferred way to do this, rather than write_frame:

df.to_sql(con=con, name='table_name_for_df', if_exists='replace', flavor='mysql')

Also note: the syntax may change in pandas 0.14...

You can set up the connection with MySQLdb:

from pandas.io import sql
import MySQLdb

con = MySQLdb.connect()  # may need to add some other options to connect

Setting the flavor of write_frame to 'mysql' means you can write to mysql:

sql.write_frame(df, con=con, name='table_name_for_df', 
                if_exists='replace', flavor='mysql')

The argument if_exists tells pandas how to deal if the table already exists:

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.

Although the write_frame docs currently suggest it only works on sqlite, mysql appears to be supported and in fact there is quite a bit of mysql testing in the codebase.

回答2:

Andy Hayden mentioned the correct function (to_sql). In this answer, I'll give a complete example, which I tested with Python 3.5 but should also work for Python 2.7 (and Python 3.x):

First, let's create the dataframe:

# Create dataframe
import pandas as pd
import numpy as np

np.random.seed(0)
number_of_samples = 10
frame = pd.DataFrame({
    'feature1': np.random.random(number_of_samples),
    'feature2': np.random.random(number_of_samples),
    'class':    np.random.binomial(2, 0.1, size=number_of_samples),
    },columns=['feature1','feature2','class'])

print(frame)

Which gives:

   feature1  feature2  class
0  0.548814  0.791725      1
1  0.715189  0.528895      0
2  0.602763  0.568045      0
3  0.544883  0.925597      0
4  0.423655  0.071036      0
5  0.645894  0.087129      0
6  0.437587  0.020218      0
7  0.891773  0.832620      1
8  0.963663  0.778157      0
9  0.383442  0.870012      0

To import this dataframe into a MySQL table:

# Import dataframe into MySQL
import sqlalchemy
database_username = 'ENTER USERNAME'
database_password = 'ENTER USERNAME PASSWORD'
database_ip       = 'ENTER DATABASE IP'
database_name     = 'ENTER DATABASE NAME'
database_connection = sqlalchemy.create_engine('mysql+mysqlconnector://{0}:{1}@{2}/{3}'.
                                               format(database_username, database_password, 
                                                      database_ip, database_name))
frame.to_sql(con=database_connection, name='table_name_for_df', if_exists='replace')

One trick is that MySQLdb doesn't work with Python 3.x. So instead we use mysqlconnector, which may be installed as follows:

pip install mysql-connector==2.1.4  # version avoids Protobuf error

Output:

Note that to_sql creates the table as well as the columns if they do not already exist in the database.

回答3:

You can do it by using pymysql:

For example, let's suppose you have a MySQL database with the next user, password, host and port and you want to write in the database 'data_2', if it is already there or not.

import pymysql
user = 'root'
passw = 'my-secret-pw-for-mysql-12ud'
host =  '172.17.0.2'
port = 3306
database = 'data_2'

If you already have the database created:

conn = pymysql.connect(host=host,
                       port=port,
                       user=user, 
                       passwd=passw,  
                       db=database,
                       charset='utf8')

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

If you do NOT have the database created, also valid when the database is already there:

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

conn.cursor().execute("CREATE DATABASE IF NOT EXISTS {0} ".format(database))
conn = pymysql.connect(host=host,
                       port=port,
                       user=user, 
                       passwd=passw,  
                       db=database,
                       charset='utf8')

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

Similar threads:

1. Writing to MySQL database with pandas using SQLAlchemy, to_sql
2. Writing a Pandas Dataframe to MySQL

回答4:

You might output your DataFrame as a csv file and then use mysqlimport to import your csv into your mysql.

EDIT

Seems pandas's build-in sql util provide a write_frame function but only works in sqlite.

I found something useful, you might try this

回答5:

The to_sql method works for me.

However, keep in mind that the it looks like it's going to be deprecated in favor of SQLAlchemy:

FutureWarning: The 'mysql' flavor with DBAPI connection is deprecated and will be removed in future versions. MySQL will be further supported with SQLAlchemy connectables. chunksize=chunksize, dtype=dtype)

回答6:

Python 2 + 3

Prerequesites

• Pandas
• MySQL server
• sqlalchemy
• pymysql: pure python mysql client

Code

from pandas.io import sql
from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://{user}:{pw}@localhost/{db}"
                       .format(user="root",
                               pw="your_password",
                               db="pandas"))
df.to_sql(con=engine, name='table_name', if_exists='replace')

回答7:

df.to_sql(name = "owner", con= db_connection, schema = 'aws', if_exists='replace', index = >True, index_label='id')

来源：https://stackoverflow.com/questions/16476413/how-to-insert-pandas-dataframe-via-mysqldb-into-database