MySQL Connector/Python - insert python variable to MySQL table

Question

I'm trying to insert a python variable into a MySQL table within a python script but it is not working. Here is my code

add_results=("INSERT INTO account_cancel_predictions"
            "(account_id,21_day_probability,flagged)"
            "Values(%(account_id)s,%(21_day_probability)s,%(flagged)s)")

data_result={
    'account_id':result[1,0],
    '21_day_probability':result[1,1],
    'flagged':result[1,2]
}

cursor.execute(add_results,data_result)

cnx.commit()
cursor.close()
cnx.close()

This gets the error

ProgrammingError: Failed processing pyformat-parameters; 'MySQLConverter' object has no attribute '_float64_to_mysql'

However, when I replace the variable names result[1,0], result[1,1], and result[1,2] with their actual numerical values it does work. I suspect python is passing the actual variable names rather than the values they hold. How do I fix this?

Solution 1

Assuming you are using mysql.connector (I think you are), define your own converter class:

class NumpyMySQLConverter(mysql.connector.conversion.MySQLConverter):
    """ A mysql.connector Converter that handles Numpy types """

    def _float32_to_mysql(self, value):
        return float(value)

    def _float64_to_mysql(self, value):
        return float(value)

    def _int32_to_mysql(self, value):
        return int(value)

    def _int64_to_mysql(self, value):
        return int(value)

config = {
    'user'    : 'user',
    'host'    : 'localhost',
    'password': 'xxx',
    'database': 'db1'
}

conn = mysql.connector.connect(**config)
conn.set_converter_class(NumpyMySQLConverter)

Solution 2

One of your passed values could be of type numpy.float64 which is not recognized by the MySQL connector. Cast it to a genuine python float on populating the dict.

Comments

[theBigChalk]

connection = engine.connect() connection.execute(""" update Players set Gold =(?) where Name=(?)""",(gold,name)) , maybe just a fanboy thing but I tend to use sqlalchemy with python and this tends to simplify much of this and I've never had issues using wildcards with it

[regeirk]

Nice solution! However, I had to include a __init__ function in order for it to work. It might be because of my version. I used something similar to the original MySQLConverter class in conversion.py.

[Evan]

Where does one put this code? In a Jupyter notebook, in the mysql-connector library... ? I'm not familiar enough with mysql-connector or OOP in general to know. LIkewise, where would an __init__ go? See also: stackoverflow.com/questions/25093950/…

[Trent Yarosevich]

It can be annoying (in my opinion) to deal with spinning up cloud resources that support mysqlclient if the use-case doesn't require the C++ optimization. This is a niche scenario, but I'd rather wrangle my data types than deal with mysql installation in serverless resources if I don't need to.