Today I ran into a funny situation. I was using sqlite3, this is my first time to use it. I was just to execute a very simple SQL statement, that looks like,

connection.execute('INSERT INTO table_name (column_name) VALUES (?)', 'column_value')

If you have run similar statement, you probably won't forget the result of above statement. I have to admit that I didn't read sqlite3 with much care. I got an error message saying the statement has 1 parameter but I pass 12 parameters to it.

Even you haven't run into this, you probably can guess what the problem is. sqlite3 do len('column_value') without knowing its type. I tried to use another way, tuple, then I found out that I didn't know one fact of tuple.

Now, here is a list, please answer by reading this script:

#!/usr/bin/python

quiz = [
    [],
    {},
    (),
    '12345',
    [12345],
    ['12345'],
    (12345),
    ('12345'),
    ('12345',),
    ]

for q in quiz:
    print '%10s ->' % repr(q),
    try:
        print len(q)
    except Exception, e:
        print e

Answers (select them to read):

[] -> 0
        {} -> 0
        () -> 0
   '12345' -> 5
   [12345] -> 1
 ['12345'] -> 1
     12345 -> object of type 'int' has no len()
   '12345' -> 5
('12345',) -> 1

So here is right way to do:

connection.execute('INSERT INTO table_name (column_name) VALUES (?)', ('column_value',))