Description
Deal -- python library for design by contract (DbC) programming. That's nice assert statements in decorators style to validate function input, output, available operations and object state. Goal is make testing much easier and detect errors in your code that occasionally was missed in tests.
Deal alternatives and similar packages
Based on the "Functional Programming" category.
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PyContracts
PyContracts is a Python package that allows to declare constraints on function parameters and return values. Contracts can be specified using Python3 annotations, or inside a docstring. PyContracts supports a basic type system, variables binding, arithmetic constraints, and has several specialized contracts and an extension API. -
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README
A Python library for design by contract (DbC) and checking values, exceptions, and side-effects. In a nutshell, deal empowers you to write bug-free code. By adding a few decorators to your code, you get for free tests, static analysis, formal verification, and much more. Read intro to get started.
Features
- Classic DbC: precondition, postcondition, invariant.
- Tracking exceptions and side-effects.
- Property-based testing.
- Static checker.
- Integration with pytest, flake8, sphinx, and hypothesis.
- Type annotations support.
- External validators support.
- Contracts for importing modules.
- Can be enabled or disabled on production.
- Colorless: annotate only what you want. Hence, easy integration into an existing project.
- Colorful: syntax highlighting for every piece of code in every command.
- Memory leaks detection: deal makes sure that pure functions don't leave unexpected objects in the memory.
- DRY: test discovery, error messages generation.
- Partial execution: linter executes contracts to statically check possible values.
- Formal verification: prove that your code works for all input (or find out when it doesn't).
- Fast: each code change is benchmarked and profiled.
- Reliable: the library has 100% test coverage, partially verified, and runs on production by multiple companies since 2018.
Deal in 30 seconds
# the result is always non-negative
@deal.post(lambda result: result >= 0)
# the function has no side-effects
@deal.pure
def count(items: List[str], item: str) -> int:
return items.count(item)
# generate test function
test_count = deal.cases(count)
Now we can:
- Run
python3 -m deal lintorflake8to statically check errors. - Run
python3 -m deal testorpytestto generate and run tests. - Just use the function in the project and check errors in runtime.
Read more in the documentation.
Installation
python3 -m pip install --user 'deal[all]'
Contributing
Contributions are welcome! A few ideas what you can contribute:
- Add new checks for the linter.
- Improve documentation.
- Add more tests.
- Improve performance.
- Found a bug? Fix it!
- Made an article about deal? Great! Let's add it into the
README.md. - Don't have time to code? No worries! Just tell your friends and subscribers about the project. More users -> more contributors -> more cool features.
To run tests locally, all you need is task. Run task all to run all code formatters, linters, and tests.
Thank you :heart: