Add callback method to get_resultsbaserock/liw/hack

2 files changed, 13 insertions, 2 deletions

diff --git a/bgproc.py b/bgproc.py
index c5b0a8a..f28f577 100644
--- a/bgproc.py
+++ b/bgproc.py
@@ -80,7 +80,7 @@ class BackgroundProcessing(object):
         for p in self.processes:
             p.join()
         
-    def get_results(self, block=False, block_all=False):
+    def get_results(self, block=False, block_all=False, callback=None):
         '''Return currently available results.
         
         If 'block' is True, then wait until there is at least one
@@ -89,14 +89,21 @@ class BackgroundProcessing(object):
         If no results are pending, then return an empty list, even if
         blocking is requested (because it would be an eternal block).
         
+        If ``callback`` is not None, it needs to be a function to be 
+        called instead of blocking for a result. The function must
+        return when there may be a result ready. The function gets
+        no arguments passed to it.
+        
         '''
 
         if (block or block_all) and self.pending == 0:
             return []
 
         items = []
-        do_block = block or block_all
+        do_block = (block or block_all) and callback is None
         while True:
+            if callback is not None:
+                callback()
             try:
                 item = self.results.get(do_block)
             except Queue.Empty:
diff --git a/bgproc_tests.py b/bgproc_tests.py
index 669409d..daa639c 100644
--- a/bgproc_tests.py
+++ b/bgproc_tests.py
@@ -57,3 +57,7 @@ class BackgroundProcessingTests(unittest.TestCase):
         self.assertEqual(self.bg.pending, 0)
         self.assertEqual(self.bg.get_results(block_all=True), [])
 
+    def test_calls_callback(self):
+        self.bg.get_results(callback=lambda: setattr(self, 'called', True))
+        self.assertTrue(self.called)
+