incdec.py

C-style increment and decrement operators for python.

🔴 Note- using this will override the call x.__pos__().__pos__() for ++x and x.__neg__().__neg__() for --x. 🔴
If for some reason you do want regular plusplus or negneg then just wrap it one level up like so; -(-x).
Also note the above doesn't apply to x++, x--, as those regularly raise SyntaxError.

Q&A:

q: What

a: this

#coding: incdec

i = 6
while i-- != 0:
    print(i)

print(f'eventually {i = }')

$ python tester.py
5
4
3
2
1
0
eventually i = -1

q: How

a: Remember the arguments when the walrus operator got merged? Well who's laughing now

Essentially, all it takes is just a little bit of text replacement, from a++ to the most definitely valid py (>=3.8) expression ((a, a := a+1)[0]).
Which, in similar fashion to C's ++ operator, increments in place but gets evaluated as it was before the increment.
We achieve this by simply picking out the a from a tuple of itself and itself updated.
Do note that the exact same goes ++a, --a and a-- (just taking either the first or second element corresponding to the operator being prefix or postfix).

q: But how tf do you do text replacements, I thought python didn't have macros

a: Ahhh, you see, python has great macros, they're just hidden under the innocent looking encoding scheme.
Ever seen old python codes do stuff like # -*- coding: utf-8 -*-?
Exactly. So what you can do is just implement a new codec with rules of your own, register it to the interpreter and make it run at startup (i'll detail in a bit on how). The last part his is important if, like in the code above, it would usually raise a SyntaxError, so you gotta make it there before the parser.

If you did that, voila, you got yourself whatever text replacement macros your heart desires.

q: How to run

a: Firstly if you don't know what a python .pth file is, I suggest you read this. Basically we want something to run our codec at startup. The way to do that is to:

1. Have the file that defines and registers the codec in site_packages (this could either be in your /lib/python/site_packages or the site_packages of your local virtual env, the latter is probably a better idea).
2. In the same spot, place the .pth file (that all it really does is import the codec file).

$ git clone https://github.com/dankeyy/inc-dec-py
$ cp inc-dec-py/incdec.py inc-dec-py/incdec_loader.pth <path-to-site_packages>/

And that's it really. Now you can make a new file, put the comment #coding: incdec on the first or second line, and you should be good to go (of course run your code with the same interpreter to which's site_packages you added the codec to).

credit goes to https://github.com/jonatan1609/codec for the initial idea of messing with codecs like that.