cursed-for

Adding C-style for loops to Python, because you can.

>>> for (i = 0; i < 10; i += 2):
...     print(i)
0
2
4
6
8

Installation

pip install cursed-for

Usage

Add the following # coding comment at the top of the file in which you wish to curse:

# coding: cursed_for

Then write the cursed for-loops as needed. Check this file for an example.

For an interactive REPL, type cursed-for in your terminal:

$ cursed-for
Cursed Python REPL, 3.10.4 (main, Apr  2 2022, 09:04:19) [GCC 11.2.0]
>>> x = 10
>>> for (;x > 5;x -= 3):
...     print(x)
10
7

But why?

This was made because of a cursed idea I had one night, which I put on twitter:

And although this worked, I didn't like the look of it. But using the methods I used, I was confined by Python's syntax, which really doesn't support the kind of things I'd have liked to do. But then I stumbled upon a couple of packages which gave me exactly the tools I needed to commit this atrocity.

OK, but how is this possible?

I wrote a blog on the approaches I went through to implement this.

The rough iterations that happened during the development are documented in the approach folder. It contains both the AST manipulation method, and the "truly cursed" method.

The "old way" usage

The first version (as shown in the original tweet) is also present in the repository, for archival purposes.

Note that this only really works in a REPL. To start it, run cursedfor.py in the terminal. It's a single file, you can get it by just downloading the one file if you want to.

>>> with _for(i := 0, i < 10, i += 2):
...     print(i)
0
2
4
6
8

Help, something is broken!

You can use the cursed-for-decode command to figure out what code is being generated by the module:

$ cat x.py                                                  
for (i = 1; i < 100; i += 1):
    print(i)

$ cursed-for-decode x.py
i = 1
while i < 100:
    print(i)
    i += 1

If the generated code seems wrong, file a bug report with the code snippet.