run with this
RWT (Run With This) provides on-demand dependency resolution.
- Allows declaration of dependencies at runtime.
- Downloads missing dependencies and makes their packages available for import.
- Installs packages to a special staging location such that they’re not installed after the process exits.
- Relies on pip to cache downloads of such packages for reuse.
- Supersedes installed packages when required.
- Re-uses the pip tool chain for package installation and pkg_resources for working set management.
RWT is not intended to solve production dependency management, but does aim to address the other, one-off scenarios around dependency management:
- build setup
- test runners
- just in time script running
- interactive development
RWT is a compliment to Pip and Virtualenv and Setuptools, intended to more readily address the on-demand needs and supersede some features like setup_requires.
The project is stable. Please try it in your day-to-day workflow and give your feedback at the project page.
- as script launcher
- as runtime dependency context manager
- as interactive interpreter in dependency context
- as module launcher (akin to python -m)
The examples folder in this project includes some examples demonstrating the power and usefulness of the project. Read the docs on those examples for instructions.
Let’s say you have a script that has a one-off purpose. It’s either not part of a library, where dependencies are normally declared, or it is normally executed outside the context of that library. Still, that script probably has dependencies, say on requests. Here’s how you can use rwt to declare the dependencies and launch the script in a context where those dependencies have been resolved.
First, add a __requires__ directive at the head of the script:
#!/usr/bin/env python __requires__ = ['requests'] import requests req = requests.get('https://pypi.io/project/rwt') print(req.status_code)
Then, simply invoke that script with rwt:
$ python -m rwt -- myscript.py Loading requirements using requests 200
Note that everything after the – is passed to the python invocation, so it’s possible to have a one-liner that runs under a dependency context:
$ python -m rwt requests -- -c "import requests; print(requests.get('https://pypi.io/project/rwt').status_code)" Loading requirements using requests 200
RWT also offers a painless way to run a Python interactive interpreter in the context of certain dependencies:
$ /clean-install/python -m rwt boto Loading requirements using boto >>> import boto >>>
Following the script example, you can make your setup.py file compatible with rwt by declaring your depenedencies in the __requires__ directive:
#!/usr/bin/env python __requires__ = ['setuptools', 'setuptools_scm'] import setuptools setuptools.setup( ... setup_requires=__requires__, )
When invoked with rwt, the dependencies will be assured before the script is run, or if run with setuptools, the dependencies will be loaded using the older technique, so the script is backward compatible.
You can also replace tests_require. Consider a package that runs tests using setup.py test and relies on the tests_require directive to resolve dependencies needed during testing. Simply declare your dependencies in a separate file, “test requirements.txt”:
# test requirements.txt pytest
For compatibility, expose those same requirements as tests_require in setup.py:
with open('test requirements.txt') as tr: tests_require = [ line.rstrip() for line in tr if re.match('\w+', line) ] setuptools.setup( ... tests_require=tests_require, )
Then invoke tests with rwt:
$ python -m rwt -r "test requirements.txt" -- setup.py test
While still supporting the old technique:
$ python setup.py test
RWT uses semver, so you can use this library with confidence about the stability of the interface, even during periods of great flux.
Invoke tests with setup.py test.
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