Python converting mysql query result to json

Question

I'm trying to implement REST APIs and part of it is formatting data into json. I am able to retrieve data from a mysql database, however the object i receive is not what I expect. here is my code

from flask import Flask
from flask.ext.mysqldb import MySQL

app = Flask(__name__)
app.config['MYSQL_HOST'] = '127.0.0.1'
app.config['MYSQL_USER'] = 'root'
app.config['MYSQL_PASSWORD'] = 'password'
app.config['MYSQL_DB'] = 'hello_db'
mysql = MySQL(app)

@app.route('/hello')
def index():
   cur = mysql.connection.cursor()
   cur.execute('''SELECT * FROM Users WHERE id=1''')
   rv = cur.fetchall()
   return str(rv)

if __name__ == '__main__':
   app.run(debug=True)

Outcome:

((1L, u'my_username', u'my_password'),)

How do I achieve to return a json format like this:

{
 "id":1, 
 "username":"my_username", 
 "password":"my_password"
}

Answer 1

You can use cursor description to extract row headers: row_headers=[x[0] for x in cursor.description] after the execute statement. Then you can zip it with the result of sql to produce json data. So your code will be something like:

from flask import Flask
from flask.ext.mysqldb import MySQL
import json
app = Flask(__name__)
app.config['MYSQL_HOST'] = '127.0.0.1'
app.config['MYSQL_USER'] = 'root'
app.config['MYSQL_PASSWORD'] = 'password'
app.config['MYSQL_DB'] = 'hello_db'
mysql = MySQL(app)

@app.route('/hello')
def index():
   cur = mysql.connection.cursor()
   cur.execute('''SELECT * FROM Users WHERE id=1''')
   row_headers=[x[0] for x in cur.description] #this will extract row headers
   rv = cur.fetchall()
   json_data=[]
   for result in rv:
        json_data.append(dict(zip(row_headers,result)))
   return json.dumps(json_data)

if __name__ == '__main__':
   app.run(debug=True)

In the return statement you can use jsonify instead of json.dumps as suggested by RickLan in the comments.

Answer 2

There is, perhaps, a simpler way to do this: return a dictionary and convert it to JSON.

Just pass dictionary=True to the cursor constructor as mentioned in MySQL's documents.

import json
import mysql.connector

db = mysql.connector.connect(host='127.0.0.1',
                             user='admin',
                             passwd='password',
                             db='database',
                             port=3306)

# This line is that you need
cursor = db.cursor(dictionary=True)

name = "Bob"
cursor.execute("SELECT fname, lname FROM table WHERE fname=%s;", (name))

result = cursor.fetchall()

print(f"json: {json.dumps(result)}")

Which will print -

json: [{'fname': "Bob", 'lname': "Dole"}, {'fname': "Bob", 'lname': "Marley"}]

(Assuming those Bobs are in the table.)

Note that types are preserved this way, a good thing, BUT will need to be transformed, parsed, or serialized into a string; for instance, if there is a date, the SQL query may return a datetime object, which will need to be parsed or serialized depending on your next step. A great way to serialize is in this answer.

Answer 3

From your output it seems like you are getting a tuple back? In which case you should be able to just map it.

from flask import Flask, jsonify
from flask.ext.mysqldb import MySQL

app = Flask(__name__)
app.config['MYSQL_HOST'] = '127.0.0.1'
app.config['MYSQL_USER'] = 'root'
app.config['MYSQL_PASSWORD'] = 'password'
app.config['MYSQL_DB'] = 'hello_db'
mysql = MySQL(app)

@app.route('/hello')
def index():
   cur = mysql.connection.cursor()
   cur.execute('''SELECT * FROM Users WHERE id=1''')
   rv = cur.fetchall()
   payload = []
   content = {}
   for result in rv:
       content = {'id': result[0], 'username': result[1], 'password': result[2]}
       payload.append(content)
       content = {}
   return jsonify(payload)

if __name__ == '__main__':
   app.run(debug=True)