1 files changed, 40 insertions, 0 deletions
diff --git a/tqdm/contrib/utils_worker.py b/tqdm/contrib/utils_worker.py
new file mode 100644
index 0000000..17adda6
--- /dev/null
+++ b/tqdm/contrib/utils_worker.py
@@ -0,0 +1,40 @@
+"""
+IO/concurrency helpers for `tqdm.contrib`.
+"""
+from __future__ import absolute_import
+
+from collections import deque
+from concurrent.futures import ThreadPoolExecutor
+
+from ..auto import tqdm as tqdm_auto
+
+__author__ = {"github.com/": ["casperdcl"]}
+__all__ = ['MonoWorker']
+
+
+class MonoWorker(object):
+    """
+    Supports one running task and one waiting task.
+    The waiting task is the most recent submitted (others are discarded).
+    """
+    def __init__(self):
+        self.pool = ThreadPoolExecutor(max_workers=1)
+        self.futures = deque([], 2)
+
+    def submit(self, func, *args, **kwargs):
+        """`func(*args, **kwargs)` may replace currently waiting task."""
+        futures = self.futures
+        if len(futures) == futures.maxlen:
+            running = futures.popleft()
+            if not running.done():
+                if len(futures):  # clear waiting
+                    waiting = futures.pop()
+                    waiting.cancel()
+                futures.appendleft(running)  # re-insert running
+        try:
+            waiting = self.pool.submit(func, *args, **kwargs)
+        except Exception as e:
+            tqdm_auto.write(str(e))
+        else:
+            futures.append(waiting)
+            return waiting