I have the following Python code:
cursor.execute("INSERT INTO table VALUES var1, var2, var3,")
where var1
is an integer, var2
and 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
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'
cur.execute("SELECT * FROM stocks WHERE symbol = '%s'" % symbol)
# Do this instead
t = ('RHAT',)
cur.execute('SELECT * FROM stocks WHERE symbol=?', t)
print(cur.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),
]
cur.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))
http://www.amk.ca/python/writing/DB-API.html
Be careful when you simply append values of variables to your statements: Imagine a user naming himself ';DROP TABLE Users;'
-- That's why you need to use SQL escaping, which Python provides for you when you use cursor.execute
in a decent manner. Example in the URL is:
cursor.execute("insert into Attendees values (?, ?, ?)", (name, seminar, paid))
The syntax for providing a single value can be confusing for inexperienced Python users.
Given the query
INSERT INTO mytable (fruit) VALUES (%s)
Generally*, the value passed to cursor.execute
must wrapped in an ordered sequence such as a tuple or list even though the value itself is a singleton, so we must provide a single element tuple, like this: (value,)
.
cursor.execute("""INSERT INTO mytable (fruit) VALUES (%s)""", ('apple',))
Passing a single string
cursor.execute("""INSERT INTO mytable (fruit) VALUES (%s)""", ('apple'))
will result in an error which varies by the DB-API connector, for example
TypeError: not all arguments converted during string formatting
sqlite3.ProgrammingError: Incorrect number of bindings supplied. The current statement uses 1, and there are 5 supplied
mysql.connector.errors.ProgrammingError: 1064 (42000): You have an error in your SQL syntax;
* The pymysql connector handles a single string parameter without erroring. However it's better to wrap the string in a tuple even if it's a single because
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?
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