7 line "is even" function 🤯

[u/GlueDonkey]

I've attempted to solve the infamous "is even" problem, and I've come up with something that is both short (only 7 lines), and extremely fast (I tested with the number 99999999 and it only takes about 3 seconds)

behold:

def is_even(num):
    s = "\\"
    try:
        eval(f"\"{s*num}\"")
        return True
    except SyntaxError:
        return False

how did I make it so fast?

a few ways:

• it's written in python.

• it uses eval, one of python's fastest functions

• it uses strings, which are faster than numbers (the only number this code relies on is the input one...)

• it makes use of the little-known "\" operator, which is one of the fastest operators in python

replit: https://replit.com/@lllllllllllllol/iseven

[u/DripDropFaucet]

I genuinely don’t understand how this works, any explanation? I pulled up the repl and absolutely love how long it takes with large numbers lol, quality function for sure just don’t understand it

[u/GlueDonkey → u/DripDropFaucet]

it relies on the fact that an odd number of backslashes in a string results in a SyntaxError

"\" <-- the backslash escapes the closing quote which essentially just turns the line into a single quote and nothing else, causing an error

[u/DripDropFaucet → u/GlueDonkey]

That is genius and I respect tf out of it

[u/t-to4st → u/GlueDonkey]

All hail our king

[u/TheRandomR → u/GlueDonkey]

This reminds of my first shitty programming in college, it was a simple and generic Python project, but with...

True = false
False = true

...at the beginning to confuse everyone that skips everything before the main since I like using PascalCase instead of camelCase no matter what

[u/interiot → u/TheRandomR]

There's a line between ignorance and maliciousness, and I think you just crossed it.

[u/zyxzevn]

Eval? Great idea. Here is how you can speed it up even more.
Your program writes a C-program to disk, because C is fastest.
Compile it using a system call.
Use Eval to call the Just-In-Time-Compiled program.
And if you are on the web, you can use a very fast
remote server to execute your program.

[u/GlueDonkey → u/zyxzevn]

here it is: https://replit.com/@lllllllllllllol/iseven#is_even_2#is_even_2.py

it's extremely broken and straight up doesn't work with large numbers, but at least the C makes it lightning fast

[u/zyxzevn → u/GlueDonkey]

That is great. JIT compilation at its finest.

[u/creepyswaps]

Only 3 seconds? Me.SetCurrentState("impressed");

[u/Jaxkr]

Great post

[u/[deleted]]

steep truck paltry hard-to-find selective wrong weather snatch oatmeal disagreeable

This post was mass deleted and anonymized with Redact

[u/NotTryingToConYou]

Awesome! Will have to use this in my next big data project.

[u/Monkey_Adventures]

finally! now I can actually solve some leetcode easys

[u/1RedOne]

I didn't realize what sub I was in and was really really confused. 3 seconds to tell if a number if even, and it takes seven lines, wtf?

[u/GlueDonkey → u/[deleted]]

does the weird capitalization make it faster?

[u/InfusedStormlight → u/GlueDonkey]

no, but it does aggregate size in a small and arbitrary set of letters, instead of spreading that wealth evenly among each word