PyVCG - Verification Condition Generator

1.0.10 verified Mon Apr 27 auth: no python

A Python library for generating verification conditions (VCs) from an intermediate language (IL) and emitting SMTLIB or interacting with solvers like CVC5 and Z3. Current version 1.0.10, supports Python 3.8+. Release cadence: irregular, with several minor releases in 2023-2024.

pip install pyvcg

Common errors

error ImportError: cannot import name 'Solver' from 'pyvcg' ↓

cause Old versions or wrong import path; Solver is in the top-level __init__.py.

fix

Use: from pyvcg import Solver

error pyvcg.exceptions.Recursion: Cycle detected in AST ↓

cause You constructed a recursive tree (cycle) which is forbidden since version 1.0.9.

fix

Ensure the AST is a DAG. For self-recursive records, use the add_component method with the record sort itself.

error ValueError: Unsupported Python version. Only Python 3.8 to 3.10 are supported. ↓

cause Old versions of pyvcg (<1.0.8) relied on CVC5 with limited Python support.

fix

Upgrade to pyvcg >=1.0.8 which supports Python 3.11+.

error OSError: libcvc5.so: cannot open shared object file ↓

cause Missing CVC5 native library or incompatible version.

fix

Install cvc5: pip install cvc5 (ensure version matches PyVCG requirements). On Windows, use pyvcg >=1.0.7.

Warnings

breaking Recursive trees are rejected since version 1.0.9. Attempting to create a cyclic AST raises pyvcg.Recursion. ↓

fix Ensure your AST is a DAG; reuse nodes only without cycles.

deprecated The CVC5 API driver is being phased out in favor of SMTLIB-based driver. The CVC5 API driver may stop working in future releases. ↓

fix Use the SMTLIB driver: set driver='smtlib' when creating Solver.

gotcha CVC5 version 1.0.7 is broken. PyVCG 1.0.3 pins to CVC5 1.0.5. Always match PyVCG's cvc5 dependency version. ↓

fix Use pip install 'cvc5==1.0.5' with PyVCG 1.0.3 or upgrade to a newer PyVCG.

gotcha String literals in SMTLIB output are escaped incorrectly in versions <1.0.2. Non-printable characters and quotes may cause solver parsing errors. ↓

fix Upgrade to pyvcg >=1.0.2.

Imports

Solver
wrong
```
from pyvcg.solver import Solver
```
correct
```
from pyvcg import Solver
```
Solver is directly exported from pyvcg, not a submodule

Literal

wrong

from pyvcg.literal import Literal

correct

from pyvcg import Literal

Literal is a top-level export

Sort
```
from pyvcg import Sort
```
Sort is directly available
Record
```
from pyvcg import Record
```
Top-level export

Quickstart

Create a solver, add a boolean assertion, and check satisfiability.

from pyvcg import Solver, Literal, Sort

solver = Solver()
# Create a boolean constant
p = Literal('p', Sort.Bool)
solver.assert_formula(p)
result = solver.check()
print(result)