Pickora 🐰

A small compiler that can convert Python scripts to pickle bytecode.

Requirements

• Python 3.8+

No third-party modules are required.

Usage

usage: pickora.py [-h] [-d] [-r] [-l {none,python,pickle}] [-o OUTPUT] file

A toy compiler that can convert Python scripts to pickle bytecode.

positional arguments:
  file                  the Python script to compile

optional arguments:
  -h, --help            show this help message and exit
  -d, --dis             disassamble compiled pickle bytecode
  -r, --eval, --run     run the pickle bytecode
  -l {none,python,pickle}, --lambda {none,python,pickle}
                        choose lambda compiling mode
  -o OUTPUT, --output OUTPUT
                        write compiled pickle to file

Lambda syntax is disabled (--lambda=none) by default.

For exmple, you can run:

python3 pickora.py -d samples/hello.py -o output.pkl

to compile samples/hello.py to output.pkl and show the disassamble result of the compiled pickle bytecode.

But this won't run the pickle for you. If you want you should add -r option, or execute the following command after compile:

python3 -m pickle output.pkl

Special Syntax

RETURN

RETURN is a keyword reserved for specifying pickle.load(s) result. This keyword should only be put in the last statement alone, and you can assign any value / expression to it.

For example, after you compile the following code and use pickle.loads to load the compiled pickle, it returns a string 'INT_MAX=2147483647'.

# source.py
n = pow(2, 31) - 1
RETURN = "INT_MAX=%d" % n

It might look like this:

$ python3 pickora.py source.py -o output.pkl
Saving pickle to output.pkl

$ python3 -m pickle output.pkl
'INT_MAX=2147483647'

Todos

• Operators (compare, unary, binary, subscript)
• Unpacking assignment
• Augmented assignment
• Macros (directly using GLOBAL, OBJECT bytecodes)
• Lambda (I don't want to support normal function, because it seems not "picklic" for me)
  • Python bytecode mode
  • Pickle bytecode mode

Impracticable

• Function call with kwargs
  • NEWOBJ_EX only support type object (it calls __new__)

FAQ

What is pickle?

RTFM.

Why?

It's cool.

Is it useful?

No, not at all, it's definitely useless.

So, is this garbage?

Yep, it's cool garbage.

Would it support syntaxes like if / while / for ?

No. All pickle can do is just simply define a variable or call a function, so this kind of syntax wouldn't exist.

But if you want to do things like:

ans = input("Yes/No: ")
if ans == 'Yes':
  print("Great!")
elif ans == 'No':
  exit()

It's still achievable! You can rewrite your code to this:

from functools import partial
condition = {'Yes': partial(print, 'Great!'), 'No': exit}
ans = input("Yes/No: ")
condition.get(ans, repr)()

ta-da!

For the loop syntax, you can try to use map / reduce ... .

And yes, you are right, it's functional programming time!