Implement background spinners

README.rst

@@ -88,6 +88,16 @@ For actions with an unknown number of steps you can use a spinner. ::
         # Do some work
         spinner.next()
 
+Spinners can run in the background, for example, during a long, blocking
+call. They will automatically be advanced with a customizable frequency
+controlled by the ``frequency`` keyword argument (0.1 seconds by default)
+This behvaior is available using the ``with`` statement. ::
+
+    from progress.spinner import Spinner
+
+    with Spinner('Loading ', frequency=0.1):
+        # Do some work, or make a blocking call
+
 There are 4 predefined spinners:
 
 - Spinner

progress/__init__.py

@@ -19,6 +19,7 @@
 from math import ceil
 from sys import stderr
 from time import time
+from threading import Thread, Event
 
 
 __version__ = '1.2'
@@ -78,6 +79,24 @@ def iter(self, it):
             self.next()
         self.finish()
 
+    def _run(self):
+        frequency = getattr(self, 'frequency', 0.1)
+        while not self._event.is_set():
+            self.next()
+            self._event.wait(frequency)
+
+    def __enter__(self):
+        self.start()
+        self._event = Event()
+        self._thread = Thread(target=self._run)
+        self._thread.start()
+
+    def __exit__(self, exc_type, exc_value, exc_tb):
+        self._event.set()
+        self._thread.join()
+        self.finish()
+
+
 
 class Progress(Infinite):
     def __init__(self, *args, **kwargs):

test_progress.py

@@ -37,3 +37,7 @@
     bar.goto(randint(0, 100))
     sleep(0.1)
 bar.finish()
+
+with Spinner('ThreadedSpinner '):
+    sleep(3)
+print()