reiter

Wrapper for Python iterators and iterables that implements a list-like random-access interface by caching retrieved items for later reuse.

Installation and Usage

This library is available as a package on PyPI:

python -m pip install reiter

The library can be imported in the usual way:

import reiter
from reiter import reiter

Examples

This library makes it possible to wrap any iterator or iterable object within an interface that enables repeated iteration over -- and random access by index of -- the items contained within that object. A reiter instance yields the same sequence of items as the wrapped iterator or iterable:

>>> from reiter import reiter
>>> xs = iter([1, 2, 3])
>>> ys = reiter(xs)
>>> list(ys)
[1, 2, 3]

Unlike iterators and some iterable objects (including those that are built-in and those that are user-defined), an instance of the reiter class always allows iteration over its items any number of times. More specifically, every invocation of iter (explicit or implicit) returns an iterator that begins iteration from the first item found in the originally wrapped iterator or iterable:

>>> list(iter(ys)), list(iter(ys))
([1, 2, 3], [1, 2, 3])
>>> list(ys), list(ys)
([1, 2, 3], [1, 2, 3])

Furthermore, it is also possible to access elements by their index:

>>> xs = iter([1, 2, 3])
>>> ys = reiter(xs)
>>> ys[0], ys[1], ys[2]
(1, 2, 3)

The built-in Python next function is also supported, and any attempt to retrieve an item once the sequence of items is exhausted raises the StopIteration exception in the usual manner:

>>> xs = reiter(iter([1, 2, 3]))
>>> next(xs), next(xs), next(xs)
(1, 2, 3)
>>> next(xs)
Traceback (most recent call last):
  ...
StopIteration

However, all items yielded during iteration can be accessed by their index, and it is also possible to iterate over those items again:

>>> xs[0], xs[1], xs[2]
(1, 2, 3)
>>> [x for x in xs]
[1, 2, 3]

Retrieval of yielded items using slice notation is also supported via the __getitem__ method:

>>> xs = reiter(iter([1, 2, 3]))
>>> xs[0:2]
[1, 2]

Instances of reiter support additional inspection methods, as well. For example, the has method returns a boolean value indicating whether a next item is available and the length method returns the length of the sequence of items emitted by the instance (once no more items can be emitted):

>>> xs = reiter(iter([1, 2, 3]))
>>> xs.has(), xs.has(), xs.has(), xs.has()
(True, True, True, False)
>>> xs.length()
3

Development

All installation and development dependencies are fully specified in pyproject.toml. The project.optional-dependencies object is used to specify optional requirements for various development tasks. This makes it possible to specify additional options (such as docs, lint, and so on) when performing installation using pip:

python -m pip install .[docs,lint]

Documentation

The documentation can be generated automatically from the source files using Sphinx:

python -m pip install .[docs]
cd docs
sphinx-apidoc -f -E --templatedir=_templates -o _source .. && make html

Testing and Conventions

All unit tests are executed and their coverage is measured when using pytest (see the pyproject.toml file for configuration details):

python -m pip install .[test]
python -m pytest

Alternatively, all unit tests are included in the module itself and can be executed using doctest:

python src/reiter/reiter.py -v

Style conventions are enforced using Pylint:

python -m pip install .[lint]
python -m pylint src/reiter

Contributions

In order to contribute to the source code, open an issue or submit a pull request on the GitHub page for this library.

Versioning

The version number format for this library and the changes to the library associated with version number increments conform with Semantic Versioning 2.0.0.

Publishing

This library can be published as a package on PyPI by a package maintainer. First, install the dependencies required for packaging and publishing:

python -m pip install .[publish]

Ensure that the correct version number appears in pyproject.toml, and that any links in this README document to the Read the Docs documentation of this package (or its dependencies) have appropriate version numbers. Also ensure that the Read the Docs project for this library has an automation rule that activates and sets as the default all tagged versions. Create and push a tag for this version (replacing ?.?.? with the version number):

git tag ?.?.?
git push origin ?.?.?

Remove any old build/distribution files. Then, package the source into a distribution archive:

rm -rf build dist src/*.egg-info
python -m build --sdist --wheel .

Finally, upload the package distribution archive to PyPI:

python -m twine upload dist/*

lapets/reiter