You can also use the set-comprehension syntax, which functions equivalently but looks slightly nicer:

    return {w for w in words if w in WORDS}

could have also directly used the intersection operator on the sets:

    return words & WORDS

or slightly more verbose, but maybe more clear for colleagues who don't regularly use sets in Python:

    return words.intersection(WORDS)

> return words & WORDS

Not quite. It'd have to be set(WORDS) instead of WORDS -- which'd be expensive. Or WORDS.keys(), which I'm not sure about -- I'd have to benchmark it.

You would only need to do set(WORDS) once at the beginning of the program, so its amortized cost is low.

I wouldn't worry about the expense of set construction vs the expense of an n-squared algorithm.

caught me, I hadn't read through the article, wasn't sure whether or not WORDS was a set or a dict. Like desdiv points out, this isn't a big deal, you can maintain an equivalent WORDS structure that is a set.

That was one of the phrases used in the program that taught me to touch type. Stuck with me for decades..and has been almost as useful to me as learning to touch type...

that is a great idiom. i remember the first time i saw it (possibly in is very essay), i thought it was awesome. I use it all over the place now. it is similiar to the javascript ternary operator [1], which I also find to be very useful

   var varX = (boolean) ? 'X' : 'Y'

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

Pretty much every language has a ternary conditional operator: C++, Java, Python, C#, Ruby....

This isn't the Python ternary which is:

  varX = 'X' if boolean else 'Y'

  # And is chainable in a more natural way than C*:
  varX = 'X' if boolean else 'Y' if other else 'Z'