MySQLdb, problem with query with user-defined variables

[buran]

I have SQL query I try to run using MySQL-python.
My code

import MySQLdb as mdb

   
def mysql_query(sql, schema='my_schema', do_commit=False):
    server, username, password = get_db_credentials('mysql')
    try:
        with mdb.connect(host=server, user=username, passwd=password, db='my_schema', charset='utf8') as cursor:
            cursor.execute(sql)
            # cursor.callproc('irr', ())
            if do_commit:
                conn.commit()
                return True
            else:
                res = cursor.fetchall()
                return (res,'')
    except mdb.Error, e:
        return([],'Error {} : {}'.format(e.args[0],e.args[1]))
        
# sql = 'call my_schema.irr()'
sql = '''
SET @runtot:=0.0;
SET @runtot_bv:=0.0;
SET @interest_exp:=0.0;
SET @daily_interest_expense:=0.0;
SELECT
   q1.value_date AS 'Value Date',
   q1.cash_flow AS 'Cash Flow',
   @runtot := @runtot + q1.cash_flow as 'Cash Flow Running Total',
   @daily_interest_expense := (@runtot_bv + q1.cash_flow)*(q1.daily_irr) AS 'Daily Interest Expense',
   (CASE WHEN DAYOFYEAR(q1.value_date) = 1 then @interest_exp := @daily_interest_expense
    ELSE @interest_exp := @interest_exp + @daily_interest_expense end) as 'Yearly Interest Expense',
   @runtot_bv := (@runtot_bv + q1.cash_flow)*(1+q1.daily_irr) as 'Balance Sheet Value'
FROM
   cash_flow AS q1;
'''
res = mysql_query(sql)
for row in res:
    print row

I got MySQL error
Error 2014: Commands out of sync; you can't run this command now.

I have no problem to run queries without user-defined variables. Tried to put the sql in stored procedure and call it two different ways (see commented lines), but get the same error.

Both sql query and the stored procedure work as expected in MySQL workbench.

Any ideas greatly appreciated. I'm reading different solutions re this error in the last couple of hours, but without success.