Set the datasource on grafana dashboards

setDatasource.py

#!/usr/bin/env python

import sqlite3
import json

"""
Quick quick script to set the datasource for grafana dashboards
"""

OLD_DATASOURCE = 'null'
NEW_DATASOURCE = 'graphite'
SQLITE_DB = '/opt/grafana/data/grafana.db'
conn = None

try:
    conn = sqlite3.connect(SQLITE_DB)
    cur = conn.cursor()

    cur.execute('SELECT id, data FROM dashboard;')

    data = cur.fetchall()
except:
    raise

for dash_id, dash_data in data:
    dash = json.loads(dash_data)

    for row in dash['rows']:
        for panel in row['panels']:
            try:
                datasource = panel['datasource']
            except KeyError:
                print("Skipping dashboard: {}, row: {}, panel: {}".format(
                    dash['title'], row['title'], panel['title']))
            if not datasource or datasource == OLD_DATASOURCE:
                print("Updating dashboard: {}, row: {}, panel: {}".format(
                    dash['title'], row['title'], panel['title']))
                panel['datasource'] = NEW_DATASOURCE

                cur.execute("UPDATE dashboard SET data=? WHERE id=?", (json.dumps(dash), dash_id))

Hello folks!
I found an easy way to change data source for all dashboards. The method below tested only on sqlite database and grafana version 7.0.1.
Make a backup of grafanadb
cp grafana.db grafana.db.backup
connect to current database
sqlite3 grafana.db
execute sql query
update dashboard set data = replace(data,'"Graphite"','null');
where Graphite is the name of datasource which you want to replace and null means default datasource in grafana.