added the attempt decorator

README.md

@@ -10,10 +10,14 @@ Makes it more convenient to run awaitable objects in concurrent batches.
 
 ## Decorators
 
-### in_async_session
+### @in_async_session
 
 Handles starting and closing of a temporary `aiohttp.ClientSession` instance around any async function that makes use of such an object to perform requests.
 
+### @attempt
+
+Allows defining for an async function to be called repeatedly if it throws a specific kind of exception.
+
 ## Building
 
 Clone this repo, install `build` via pip, then run `python -m build` from the repository's root directory. This should produce a `dist/` subdirectory with a wheel (build) and archive (source) distribution. 

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = webutils-df
-version = 0.0.5
+version = 0.0.6
 author = Daniil F.
 author_email = mail@placeholder123.to
 description = Miscellaneous web utilities

src/webutils/util.py

@@ -2,7 +2,9 @@ import logging
 import asyncio
 from functools import wraps
 from inspect import signature
-from typing import Callable, Awaitable, Dict, Tuple, Any, TypeVar
+from math import inf
+from timeit import default_timer
+from typing import Callable, Awaitable, Dict, Tuple, Sequence, Any, Type, Union, TypeVar
 
 from aiohttp.client import ClientSession
 
@@ -11,6 +13,7 @@ LOGGER_NAME = 'webutils'
 logger = logging.getLogger(LOGGER_NAME)
 
 AsyncFunction = TypeVar('AsyncFunction')
+AttemptCallbackT = Callable[[AsyncFunction, Exception, int, float, tuple, dict], Awaitable[None]]
 
 
 def _get_param_idx_and_default(function: Callable, param_name: str) -> Tuple[int, Any]:
@@ -85,6 +88,65 @@ def in_async_session(_func: AsyncFunction = None, *,
     return decorator if _func is None else decorator(_func)
 
 
+def attempt(_func: AsyncFunction = None, *,
+            exception: Union[Type[Exception], Sequence[Type[Exception]]] = Exception,
+            max_attempts: float = inf,
+            timeout_seconds: float = inf,
+            seconds_between: float = 0,
+            callback: AttemptCallbackT = None) -> AsyncFunction:
+    """
+    Decorator allowing an async function to be called repeatedly, if previous attempts cause specific exceptions.
+    Note: If no limiting arguments are passed to the decorator, the decorated function **will** be called repeatedly in
+    a potentially infinite loop, as long as it keeps throwing an exception.
+
+    Args:
+        _func:
+            Control parameter; allows using the decorator with or without arguments.
+            If this decorator is used *with any* arguments, this will always be the decorated function itself.
+        exception (optional):
+            An `Exception` (sub-)class or a sequence thereof; a failed call of the decorated function will only be
+            repeated if it fails with a matching exception. Defaults to `Exception`, i.e. any exception.
+        max_attempts (optional):
+            The maximum number of (re-)attempts at calling the decorated function; if it is called `max_attempts` times
+            and fails, the exception will be propagated. The number of attempts is unlimited by default.
+        timeout_seconds (optional):
+            Defines the cutoff time (in seconds) for the entirety of attempts at executing the decorated function;
+            if the attempts take longer in total and fail, the exception will be propagated. No timeout by default.
+        seconds_between (optional):
+            Sets a sleep interval (in seconds) between each attempt to call the decorated function. Defaults to 0.
+        callback (optional):
+            If passed an async function (with matching parameters), a failed **and caught** attempt will call it with
+            the following positional arguments (in that order):
+            - the decorated async function itself
+            - the exception class encountered and caught
+            - the total number of failed attempts up to that point
+            - the `seconds_between` argument
+            - positional and keyword arguments (as tuple and dictionary respectively) passed to the decorated function
+
+    Raises:
+        Any exceptions that do **not** match those passed to the `exception` parameter are immediately propagated.
+        Those that were specified in `exception` are propagated when `max_attempts` or `timeout_seconds` are reached.
+    """
+    def decorator(function: AsyncFunction) -> AsyncFunction:
+        # Using `functools.wraps` to preserve information about the actual function being decorated
+        # More details: https://docs.python.org/3/library/functools.html#functools.wraps
+        @wraps(function)
+        async def wrapper(*args, **kwargs) -> Any:
+            start, failed_attempts = default_timer(), 0
+            while True:
+                try:
+                    return await function(*args, **kwargs)
+                except exception as e:
+                    failed_attempts += 1
+                    if default_timer() - start >= timeout_seconds or failed_attempts >= max_attempts:
+                        raise e
+                    if callback:
+                        await callback(function, e, failed_attempts, seconds_between, args, kwargs)
+                    await asyncio.sleep(seconds_between)
+        return wrapper
+    return decorator if _func is None else decorator(_func)
+
+
 async def gather_in_batches(batch_size: int, *aws: Awaitable, return_exceptions: bool = False) -> list:
     """
     Simple extension of the `asyncio.gather` function to make it easy to run awaitable objects in concurrent batches.