The Python IAQ: Infrequently Answered Questions (opens in new tab)

     python -c "import _if; fact = lambda n: _if (n <= 1) (1) (lambda: n * fact(n-1)) ; fact(5)"

The main advantage of a 1-liner is that you can compose the whole thing and execute it without having to format anything. That is a nice feature for code that is only ever intended to be used once, such as from the python repl or some other shell. --Or more than once, for the duration of a session. It's a lot easier to use command history to get and modify a 1-liner than to replay a 5-line function definition.

When the code is primarily expressions, it's relatively easy to to this. Trying to do one-liners with regular python syntax can get tricky.

Also, if you have a series of similar relationships to present, it's often easier to line them up next to each other. You might cut 12 lines to 6 lines and the whole thing will be far clearer. Although in those cases, it's probably more effective to use a dictionary to achieve the same thing, with the advantage of data/logic separation.

Sometimes I put short ifs in one line, just personal taste

    def fact(n):
        if n<=1: return 1
        else:    return n * fact(n-1)

They are of broadly equivalent complexity (if you are used to Python) and you can fit more of the former in an editor window.

I don't like tho' that "lambda" is a keyword in Python, I much prefer Haskell's \ or OCaml's fun.

   from math import factorial

Or

   fact = lambda n: reduce(operator.mul, xrange(1, n+1), 1)

I agree.

The article actually contains the "if u cn rd ths..." phrase and it's a nice touch. However, it would be better to keep the original title and mention the phrase in the comments.

I don't get it anyway, if I can read this, why can I get a job in functional programming?

It was a weird title. I did an an quick poll of two non-programmer, LOL-speak experts, and I got these answers:

- If you can read this, you can get a job in financial program (if there were any)

- If you can read this, you can get a job in functional programs/programming (if there were any)

I don't know what this proves.

Incidentally, most C-style-syntax languages have a ternary conditional operator, and I use it quite a lot for things like building strings, very small conditionals, etc.... When used correctly, it can improve readability and expressiveness quite a bit.

x = <test> ? <result> : <alternative>

Some times for slightly more complex expressions, I'll put them on separate lines so as to have a very compact if/else structure.

It's worth noting that Peter himself mentions that most of the ternary tricks he describes are not very readable and wouldn't be considered Pythonic.

   Beautiful is better than ugly.
   Explicit is better than implicit.
   Simple is better than complex.

Personally I'd hate to see something like that in any real-world project.

   (test and [result] or [alternative])[0]

As pointed out in the OP, there are actually quite a lot of ways to simulate the ternary operator in Python. An interesting one is (result, alternative)[test]. If result and alternative are functions you could write it as (result, alternative)[test]().

And for desert: I love this syntax:

  if 0 < x <= 100: pass

For more info see: http://stackoverflow.com/questions/394809/python-ternary-ope...

"..and the rise of Haskell and Clojure.."

Is there any real world evidence of said claim, outside geek-fetish bubbles like HN ?

Functional programming jobs are scarce, but that's because no-one is a "functional programmer" in the same way that you might be a "PHP programmer". Instead you get lots of jobs where you happen to write a lot of code in a functional programming language but you don't look like a programmer in an organizational sense - you're an "analyst" or an "engineer" or whatever. That's where F# is making inroads.