Python + SQLite：绑定元组列表

Question

I have an insert statement with only one parameter

INSERT OR IGNORE INTO sample (descr) VALUES (?);

And I have a list of tuples

[(a,b), (c,d)]

Now I am using

cur.executemany(query, listOfTuples)

Python doesn't like to receive 2 params, and demands only 1. What is the best way to bind all first values from the tuples with this statement?

I've tried something like

cur.executemany(query, listOfTuples[0])

But now Python thinks I am giving it 4 params.

Answer 1

Use a list comprehension to select just the first value; using a slice to create new tuples of length 1:

cur.executemany(query, [t[:1] for t in listOfTuples])

Quick demo to show the result of the list comprehension:

>>> listOfTuples = [('a', 'b'), ('c', 'd')]
>>> [t[:1] for t in listOfTuples]
[('a',), ('c',)]

You can also use a generator expression, which creates the tuple slices on the fly:

cur.executemany(query, (t[:1] for t in listOfTuples))

It could be that not all database APIs support an iterable and instead expect to be handed something that has a length though.