Metadata-Version: 1.1
Name: waiter
Version: 0.4
Summary: Delayed iteration for polling and retries.
Home-page: https://bitbucket.org/coady/waiter
Author: Aric Coady
Author-email: aric.coady@gmail.com
License: Apache Software License
Description: .. image:: https://img.shields.io/pypi/v/waiter.svg
           :target: https://pypi.python.org/pypi/waiter/
        .. image:: https://img.shields.io/pypi/pyversions/waiter.svg
        .. image:: https://img.shields.io/pypi/status/waiter.svg
        .. image:: https://img.shields.io/travis/coady/waiter.svg
           :target: https://travis-ci.org/coady/waiter
        .. image:: https://img.shields.io/codecov/c/github/coady/waiter.svg
           :target: https://codecov.io/github/coady/waiter
        
        Does Python need yet another retry / poll library?
        It needs at least one that isn't coupled to decorators and functions.
        Decorators prevent the caller from customizing delay options.
        And even organizing the code around functions prevents custom handling of failures.
        
        Waiter is built around iteration instead, because the foundation of retrying / polling is a slowly executing loop.
        The resulting interface is both easier to use and more flexible,
        decoupling the delay algorithms from the application logic.
        
        Usage
        =========================
        Supply a number of seconds to repeat endlessly, or any iterable of seconds.
        
        .. code-block:: python
        
           from waiter import wait
        
           wait(1)              # 1, 1, 1, 1, ...
           wait([1] * 3)        # 1, 1, 1
           wait([0.5, 0.5, 60]) # circuit breaker
        
        So any delay algorithm is easily created,
        but constructors for common algorithms are also provided.
        
        .. code-block:: python
        
           wait(1) + 1       # incremental backoff 1, 2, 3, 4, ...
           w = wait(1) * 2   # exponential backoff 1, 2, 4, 8, ...
           w[:3]             # limit attempt count 1, 2, 4
           w <= 5            # set maximum delay   1, 2, 4, 5, 5, 5, ...
           w.random(-1, 1)   # add random jitter
        
        Then simply use the ``wait`` object like any iterable, yielding the amount of elapsed time.
        Timeouts also supported of course.
        
        .. code-block:: python
        
           from waiter import wait, suppress, first
        
           for elapsed in wait(delays):           # first iteration is immediate
              with suppress(exception):           # then each subsequent iteration sleeps as necessary
                 ...
                 break
        
           for _ in wait(delays, timeout):        # standard convention for ignoring a loop variable
              ...                                 # won't sleep past the timeout
              if ...:
                 break
        
           results = (... for _ in wait(delays))  # expressions are even easier
           first(predicate, results[, default])   # filter for first true item
           assert any(results)                    # perfect for tests too
        
        Yes, functional versions are provided too, because now they're trivial to implement.
        The decorator variants are simply partial applications of the corresponding methods.
        Note decorator syntax doesn't support arbitrary expressions, hence the name assignment.
        
        .. code-block:: python
        
           backoff = wait(0.1) * 2
        
           backoff.repeat(func, *args, **kwargs)           # generate results
           backoff.retry(exception, func, *args, **kwargs) # return first success or re-raise exception
           backoff.poll(predicate, func, *args, **kwargs)  # return first success or raise StopIteration
        
           @backoff.repeating
           @backoff.retrying(exception)
           @backoff.polling(predicate)
        
        But in the real world:
        
        * the function may not exist or be succinctly written as a lambda
        * the predicate may not exist or be succinctly written as a lambda
        * logging may be required
        * there may be complex handling of different exceptions or results
        
        So consider the block form, just as decorators don't render ``with`` blocks superfluous.
        Also note ``wait`` objects are re-iterable provided their original delays were.
        
        Installation
        =========================
        ::
        
           $ pip install waiter
        
        Dependencies
        =========================
        * Python 2.7, 3.3+
        
        Tests
        =========================
        100% branch coverage. ::
        
           $ pytest [--cov]
        
        Changes
        =========================
        0.4
        
        * Decorators support methods
        * Iterables can be throttled
        
        0.3
        
        * Waiters behave as iterables instead of iterators
        * Support for function decorators
        
        0.2
        
        * ``suppress`` context manager for exception handling
        * ``repeat`` method for decoupled iteration
        * ``first`` function for convenient filtering
        
Keywords: wait retry poll delay sleep timeout incremental exponential backoff
Platform: UNKNOWN
Classifier: Development Status :: 5 - Production/Stable
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Apache Software License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.3
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Classifier: Topic :: Software Development :: Libraries :: Python Modules
