Convert any Python file into a single line of code

https://github.com/csvoss/oneliner

by odeke-em • 11 years ago

108 25 11 years ago

github.com

wfunction2• 11 years ago

Space: O(n). No code is ever duplicated, so the one-lined code produced is linear in the size of the input code.

Seems like a non sequitur?

philh• 11 years ago

I'm not sure why you think that. Do you mean that normally, in this context "space" means the memory usage of a program, which isn't particularly related to the size of the program?

In which case, yeah, it's a little incongruous. The "space" bit is talking about the textual representation of the program produced, while the "time" bit is talking about the runtime characteristics of the program.

csvoss• 11 years ago

Oh, you're right, I'm using "space" incorrectly. Fixed :)

wfunction2• 11 years ago

Not really, what I meant was that it's pretty easy to go over O(n) without ever duplicating any code. Like just imagine if you had a string literal that held all the numbers from 1 to n^2.

detaro• 11 years ago

For a very limited definition of "any python file".

Still brings me back to highschool, where we toyed with that kind of tricks (someone builds something, the others try to figure out how it works). Fun times!

raverbashing• 11 years ago

Yeah, like trying to do a C file without semicolons

enesunal• 11 years ago

+1 for Y Combinator :)

htor• 11 years ago

Nice.

This made me think of this video with Jim Weirich demonstrating functional patterns, transformations and the Y combinator:

https://vimeo.com/45140590

Highly recommened. It's very related to what seems to be going on here, and actually quite funny.

rplnt2• 11 years ago

Your code was not valid: 'try-except' is an open problem.

Well that was disappointing...

benzoate3• 11 years ago

Call me when the results are compliant with PEP8

StavrosK2• 11 years ago

Brrring

benzoate3• 11 years ago

haha, I think the resulting one liners are a little over 80 characters :)

amelius• 11 years ago

However, since while loops and for loops are implemented with recursion, you might encounter maximum recursion depth exceeded errors during runtime if your loops go on for too long.

Okay, this was enough to scare me away from it :)

wiz21• 11 years ago

is it me or is it continuation passing style ?

cmdrfred• 11 years ago

Import pythonfile

dahart• 11 years ago

+1 for the amusing faq. And I think this is a cool project. I'll use it just to learn better ways to make one-liners for use in other shell scripts and makefiles. Python has always been harder than the other languages I know to make one-liners, but on occasion it's quite useful.

mrks_• 11 years ago

On what occasion would a one-liner be useful? I'm genuinely curious, because I can't think of any such case, but I wouldn't doubt there being a few.

rplnt2• 11 years ago

Read the previous sentence :)

gknoy• 11 years ago

Command line use. You grep some files, and think, "man, this really needs this ONE LITTLE FILTER". So, you pipe it to `perl -e "..."`, and soon have a very short program that you iterate on a few times to make sure you have right, and then you pipe it through the rest of the toolchain.

I don't write Perl much anymore, but that was far and away my __favorite__ way to use it. I love coding in Python now, more than I ever liked programming in any language (except perhaps lisp), but I still don't feel I can use it on the command line that way.

In the context of a Python program, I can't see the value of a Lovecraftian lambda (unless maybe in code golf comments?), but I found this article very appealing mainly because it's quite a feat. Doing anything nontrivial in a lambda is a pain in the ass, so the fact that someone wrote a tool to do it is awesome.

im3w1l• 11 years ago

I formatted one of the converted examples for easier reading

http://pastebin.com/SEMHXkd6

kosievdmerwe• 11 years ago

I in the distant past when I was still in Uni attempted to do something similar, though I never finished it. I think I should take up my project again and try to finish it this time. I got stuck last time trying to figure out how to do a try/catch.

The one big thing I notice this is doing "wrong", is that it is not linear in recursion depth: Each statement increases the stack depth by 1. The way around this is to instead sequence the commands using arrays, since python guarantees the execution order is left to right. So his example could have been rewritten as:

  (lambda s: [s.__setitem__('x', 3), s.__setitem__('y', 4), print(s['x'] < s['y'] < 5)])({})

(though for this example you could just modify the result of globals())

Then you can also do trickery to get for and while loops into generator expressions as opposed to lambdas. The hard part is handling continues and breaks. For instance:

  while <cond>:
    <stmts>

can get compiled into something like

  list(<compiled_stmts> for _ in itertools.takewhile(lambda _: <compiled_cond>, itertools.cycle([1])))

(though you'll want to replace list with a function that evaluates the iterator but doesn't take up O(N) space where N is the number of iterations, something like a no-op accumulator)

To handle breaks and continues, you'd have to make your <compiled_stmts> be aware that a break/continue was called (a flag on some meta table was my plan), so they can terminate early. You'd also have to change <compiled_cond> to terminate the loop (on a break) and reset the continue flag.

phantom_oracle• 11 years ago

Why pass up a perfectly good excuse to abuse lambda functions, ternary expressions, list comprehensions, and even the occasional Y combinator? Never pass up an opportunity to use the Y combinator.

^^ Legendary

vldr• 11 years ago

First try: Your code could not be one-lined. Open problem: try-except

Second try: Your code could not be one-lined. Open problem: yield

Third try: Your code could not be one-lined. Open problem: raise

Fourth try: Your code could not be one-lined. Not yet implemented: classdef

So, any file without class definitions, try/except/raise/yield (and probably some more). Not my definition of 'any' :)

Convert any Python file into a single line of code

Related Stories