evalo 0.2.0

Reverse evaluate values to Python code using constraint solving

Python code synthesis

This project is used to interpret Python code and generate Python code based on given values.

This project is heavily influenced by Barliman, which implemented this exact idea for Scheme. While Barliman works wonders, I don't think Scheme is a programming language that is widely used in production environments. This is the reason I created this project, so that the principle of Barliman could be applied to Python.

Examples

This project can do both interpreting from Python code to values and vica versa. For example, AST values will be converted to the correct interpreted values:

> from evalo import *
> x = var()
> run(1, x, eval_expro(ast.BinOp(left=ast.Num(n=1), op=ast.Add(), right=ast.Num(n=1)), [], x))

(2,)

Interpreting from values to Python code will generate AST objects, which can be directly translated to Python code using external libraries. For example, if we want 5 different versions of Python code that are interpreted to the value 2, we can do the following:

> from evalo import *
> x = var()
> run(5, x, eval_expro(x, [], 2))

(<_ast.Num at 0x7fdf44aabe48>,
 <_ast.BinOp at 0x7fdf44a87fd0>,
 <_ast.BinOp at 0x7fdf44a1d320>,
 <_ast.BinOp at 0x7fdf44a444e0>,
 <_ast.BinOp at 0x7fdf46ee36a0>)

To translate this to human-readable values, we can use ast_dump_if_possible:

> [ast_dump_if_possible(y) for y in run(5, x, eval_expro(x, [], 2, maxdepth=3))]

['Num(n=2)',
 'BinOp(left=Num(n=0), op=Add(), right=Num(n=2))',
 'BinOp(left=Num(n=0), op=Sub(), right=BinOp(left=Num(n=0), op=Sub(), right=Num(n=2)))',
 'BinOp(left=Num(n=1), op=Mult(), right=Num(n=2))',
 'BinOp(left=BinOp(left=Num(n=0), op=Add(), right=Num(n=0)), op=Add(), right=Num(n=2))']

Using the astunparse library we can directly translate this output to Python source code:

> [astunparse.unparse(y).strip() for y in run(10, x, eval_expro(x, [], 2, maxdepth=3))]

['2',
 '(0 + 2)',
 '(0 - (0 - 2))',
 '(1 * 2)',
 '((0 + 0) + 2)',
 '((0 + 0) - (0 - 2))',
 '((1 + 0) * 2)',
 '((0 - 0) + 2)',
 '((0 - 0) - (0 - 2))',
 '((1 - 0) * 2)']

Development

If you want to help develop on this project, you can install it like so using Python 3.7:

mkvirtualenv -a $(pwd) $(basename $(pwd)) -p python3
pip install -r requirements/development.txt
pre-commit install

This project uses tox with pytest for testing, so just run tox to run all tests.