Python: Append items to a tuple

Tuples, tuples, tuples. Thats fun to say. We’ve all used them, but dynamic assembly of them? Now this is cool — and something I never needed to do until today of course. Appending values to a list, or a dict is easy and well documented, but less common is the need to append or dynamically assemble a tuple. Lets look at a Pythonic way to do that.

But why? (You should always ask this) In my use-case, I was dynamically assembling an sql query. based on the existence of a form variable, i needed to add a clause to my sql, which I am doing classic pythonic replacement on using a tuple of values.
Here is the deal — when you set your first value, simply put it in parens with a trailing comma like so:

myTuple = (‘first item’,)

Notice the trailing comma!

Now to add items to it, assign the tuple with the + operator:

myTuple = myTuple + (‘second item’,)

Again, notice the trailing comma! This works in sequential code or loops.

Now if you output your Tuple, you get:

>>> myTuple

(‘first item’, ‘second item’)

So for my use case, then I can use it in a SQL statement like so:

sql = “SELECT * from table WHERE col1=%s and col2=%s”
db.engine.execute(sql, myTuple)

There you have it. Not difficult at all, but I never came across this before, so I am blogging about it to a) help others, and b) have a place to look it up when I forgot.

Ciao