Skip to main content

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.


Popular posts from this blog

Making Macbook Air with 128GB SSD usable with Bootcamp

I recently got a new Macbook Air 11" (the 2012 version) and loaded it with goodies like 8GB ram and 2GHz Core i7.  What I DIDN'T upgrade was the internal SSD.  My config came with 128GB SSD and I refused to pay $300+ to upgrade it to 256GB.  Yeah I know, some call me cheap, but SSds cost $75-$150 for 240GB, so adding another 128GB for $300 seemed way too steep for me.  I figured "ok, I'm going to make 128G work!"

Here is the story of how that went...

Installing python 3.4.x on OSX El Capitan

I love "brew" package manager, but sometimes being too progressive breaks things.  I have several python apps that I maintain that get deployed to AWS using Elastic Beanstalk.  AWS eb can deploy with python 2.7 or 3.4.  Any recent 'brew install python3" will get 3.5.1. #annoying

Dell XPS M1330 + Snow Leopard Hackintosh

I have been working with a Dell XPS M1330 laptop for a few years now.  It doesn't quite match up to the newest notebooks in terms of performance, but it certainly still has some life in it.  I had previously installed OSX 10.5.x on it as an experiment, and had moderate success.  I decided to revisit this idea again to install Snow Leopard (OSX 10.6) on the Dell M1330, and keep some notes for those of you brave enough to Hackintosh your own machine...