add exception

satella/coding/concurrent/futures/collection.py

+import concurrent
 import typing as tp
 from concurrent.futures import Future
 
@@ -109,9 +110,34 @@ class FutureCollection:
         :param timeout: a timeout in seconds for a single result. Default value None means
             wait as long as necessary
         :return: list containing results of all futures
-        :raises TimeoutError: timeout while waiting for result
+        :raises WouldWaitMore: timeout while waiting for result
         """
-        return [fut.result(timeout) for fut in self.futures]
+        try:
+            return [fut.result(timeout) for fut in self.futures]
+        except concurrent.futures.TimeoutError:
+            raise WouldWaitMore('timeout waiting for the result')
+
+    def exception(self, timeout: tp.Optional[float] = None) -> tp.Optional[Exception]:
+        """
+        Return first exception raised by any of the futures
+
+        This will block until the results are available.
+        This call proceeding does not mean that results for all are available, since
+        this will return the first exception encountered!
+
+        :param timeout: a timeout in seconds for a single result. Default value None means
+            wait as long as necessary
+        :return: the first exception, or None if there were no exceptions
+        :raises WouldWaitMore: timeout while waiting for result
+        """
+        try:
+            for fut in self.futures:
+                e = fut.exception(timeout)
+                if e is not None:
+                    return e
+            return None
+        except concurrent.futures.TimeoutError:
+            raise WouldWaitMore('timeout waiting for the result')
 
     def cancel(self) -> bool:
         """

tests/test_coding/test_concurrent.py

@@ -19,6 +19,13 @@ from satella.exceptions import WouldWaitMore, AlreadyAllocated, Empty
 
 class TestConcurrent(unittest.TestCase):
 
+    def test_future_collection_exception(self):
+        fc = FutureCollection([PythonFuture(), PythonFuture()])
+        fc.set_running_or_notify_cancel()
+        fc[0].set_exception(IndexError())
+        fc[1].set_exception(ValueError())
+        self.assertIsInstance(fc.exception(), IndexError)
+
     def test_future_collection_callbacks_one(self):
         a = {'count': 0}