How to use variables in SQL statement in Python?

Ok so I'm not that experienced in Python.

I have the following Python code:

cursor.execute("INSERT INTO table VALUES var1, var2, var3,")

where var1 is an integer, var2 & var3 are strings.

How can I write the variable names without python including them as part of the query text?


cursor.execute("INSERT INTO table VALUES (%s, %s, %s)", (var1, var2, var3))

Note that the parameters are passed as a tuple.

The database API does proper escaping and quoting of variables. Be careful not to use the string formatting operator ( % ), because

  • it does not do any escaping or quoting.
  • it is prone to Uncontrolled string format attacks eg SQL injection.

  • Different implementations of the Python DB-API are allowed to use different placeholders, so you'll need to find out which one you're using -- it could be (eg with MySQLdb):

    cursor.execute("INSERT INTO table VALUES (%s, %s, %s)", (var1, var2, var3))
    

    or (eg with sqlite3 from the Python standard library):

    cursor.execute("INSERT INTO table VALUES (?, ?, ?)", (var1, var2, var3))
    

    or others yet (after VALUES you could have (:1, :2, :3) , or "named styles" (:fee, :fie, :fo) or (%(fee)s, %(fie)s, %(fo)s) where you pass a dict instead of a map as the second argument to execute ). Check the paramstyle string constant in the DB API module you're using, and look for paramstyle at http://www.python.org/dev/peps/pep-0249/ to see what all the parameter-passing styles are!


    Many ways. DON'T use the most obvious one ( %s with % ) in real code, it's open to attacks.

    Here copy-paste'd from pydoc of sqlite3 :

    # Never do this -- insecure!
    symbol = 'RHAT'
    c.execute("SELECT * FROM stocks WHERE symbol = '%s'" % symbol)
    
    # Do this instead
    t = ('RHAT',)
    c.execute('SELECT * FROM stocks WHERE symbol=?', t)
    print c.fetchone()
    
    # Larger example that inserts many records at a time
    purchases = [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
                 ('2006-04-05', 'BUY', 'MSFT', 1000, 72.00),
                 ('2006-04-06', 'SELL', 'IBM', 500, 53.00),
                ]
    c.executemany('INSERT INTO stocks VALUES (?,?,?,?,?)', purchases)
    

    More examples if you need:

    # Multiple values single statement/execution
    c.execute('SELECT * FROM stocks WHERE symbol=? OR symbol=?', ('RHAT', 'MSO'))
    print c.fetchall()
    c.execute('SELECT * FROM stocks WHERE symbol IN (?, ?)', ('RHAT', 'MSO'))
    print c.fetchall()
    # This also works, though ones above are better as a habit as it's inline with syntax of executemany().. but your choice.
    c.execute('SELECT * FROM stocks WHERE symbol=? OR symbol=?', 'RHAT', 'MSO')
    print c.fetchall()
    # Insert a single item
    c.execute('INSERT INTO stocks VALUES (?,?,?,?,?)', ('2006-03-28', 'BUY', 'IBM', 1000, 45.00))
    
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