hypothesmith

0.3.3 verified Fri May 01 auth: no python

Hypothesis strategies for generating Python programs, similar to CSmith. Current version 0.3.3; release cadence is low, mostly bugfixes. Requires Python >= 3.8.

pip install hypothesmith

Common errors

error ModuleNotFoundError: No module named 'hypothesmith' ↓

cause hypothesmith not installed.

fix

Run 'pip install hypothesmith'.

error hypothesis.errors.InvalidArgument: Expected a strategy, got ... ↓

cause Incorrect import path; from_grammar returns a strategy but may be called incorrectly.

fix

Ensure you use 'from hypothesmith import from_grammar' and pass valid grammar rules.

error AttributeError: module 'hypothesmith' has no attribute 'from_node' ↓

cause Using an older API that was removed or renamed.

fix

Use 'from hypothesmith import from_grammar' instead of from_node.

Warnings

gotcha The grammar strings use angle brackets around rule names (e.g., '<stmt>'), not just the rule name. ↓

fix Use '<stmt>' not 'stmt' when passing to from_grammar.

deprecated from_grammar() replaces the older from_node() API; from_node may be removed in future versions. ↓

fix Use from_grammar() instead of from_node().

gotcha Generated code may be syntactically correct but semantically invalid (e.g., referencing undefined names). ↓

fix Combine with Hypothesis strategies to generate valid names or use custom filters.

Imports

from hypothesmith import from_grammar
wrong
```
import hypothesmith; hypothesmith.from_grammar
```
correct
```
from hypothesmith import from_grammar
```
Common mistake: using module-level access instead of direct import; direct import is idiomatic.
from hypothesmith import from_grammar
wrong
```
from hypothesmith import version
```
correct
```
from hypothesmith import from_grammar, __version__
```
Version is stored as __version__ not version.

Quickstart

Generate Python code strings from grammar rules; use with Hypothesis to fuzz parsers or interpreters.

from hypothesmith import from_grammar
from hypothesis import given, strategies as st

# Generate a simple expression using Python's grammar
@given(from_grammar('<eval_input>', start='<eval_input>'))
def test_parse(code):
    assert isinstance(code, str)
    assert len(code) > 0

test_parse()