Change process to thread (#825)

Author: AlexeyKozhevin

batchflow/plotter/plot.py

@@ -5,7 +5,7 @@
 from itertools import cycle
 from numbers import Number
 from warnings import warn
-from multiprocessing import Process
+from threading import Thread
 
 import numpy as np
 
@@ -36,9 +36,9 @@ def _wrapper(*args, **kwargs):
         detach = kwargs.get('detach', False)
 
         if detach is True:
-            process = Process(target=func, args=args, kwargs=kwargs,
-                              daemon=True, name=f'daemon_for_{func.__qualname__}')
-            process.start()
+            thread = Thread(target=func, args=args, kwargs=kwargs,
+                            daemon=True, name=f'daemon_for_{func.__qualname__}')
+            thread.start()
             return None
 
         result = func(*args, **kwargs)
@@ -1691,9 +1691,9 @@ def save(self, **kwargs):
 
         if savepath:
             if detach:
-                process = Process(target=self.figure.savefig, kwargs={'fname': savepath, **save_config},
-                                  daemon=True, name=f'daemon_for_{self.save.__qualname__}')
-                process.start()
+                thread = Thread(target=self.figure.savefig, kwargs={'fname': savepath, **save_config},
+                                daemon=True, name=f'daemon_for_{self.save.__qualname__}')
+                thread.start()
             else:
                 self.figure.savefig(fname=savepath, **save_config)
 

batchflow/tests/detachable_test.py

@@ -0,0 +1,57 @@
+"""Test that the detachable decorator and Plot.save work with detach=True.
+
+The original implementation used multiprocessing.Process which fails on Python 3.14
+due to a pickling error: `@wraps(func)` preserves `__qualname__`, so pickle resolves
+`Plot.plot` by name and finds the wrapper instead of the original function.
+
+Replacing Process with Thread avoids pickling entirely — figure saving doesn't need
+process isolation.
+"""
+
+import os
+import tempfile
+
+import numpy as np
+
+
+def test_detachable_plot_with_detach():
+    """Plot.plot with detach=True should complete without PicklingError."""
+    from batchflow.plotter.plot import Plot
+
+    data = np.random.rand(10, 10)
+    with tempfile.TemporaryDirectory() as tmpdir:
+        savepath = os.path.join(tmpdir, "test_detach.png")
+        p = Plot(data=data, mode="image", show=False, detach=True, savepath=savepath)
+        # detach=True runs in a daemon thread — give it a moment to finish
+        import time
+        time.sleep(1)
+        # The plot object should have been created without error
+        assert p is not None
+
+
+def test_plot_save_with_detach():
+    """Plot.save with detach=True should complete without PicklingError."""
+    from batchflow.plotter.plot import Plot
+
+    data = np.random.rand(10, 10)
+    with tempfile.TemporaryDirectory() as tmpdir:
+        savepath = os.path.join(tmpdir, "test_save_detach.png")
+        p = Plot(data=data, mode="image", show=False, savepath=savepath)
+        assert os.path.exists(savepath)
+
+        savepath2 = os.path.join(tmpdir, "test_save_detach2.png")
+        p.save(savepath=savepath2, detach=True)
+        import time
+        time.sleep(1)
+        assert os.path.exists(savepath2)
+
+
+def test_detachable_plot_without_detach():
+    """Plot.plot with detach=False (default) should work as before."""
+    from batchflow.plotter.plot import Plot
+
+    data = np.random.rand(10, 10)
+    with tempfile.TemporaryDirectory() as tmpdir:
+        savepath = os.path.join(tmpdir, "test_no_detach.png")
+        Plot(data=data, mode="image", show=False, savepath=savepath)
+        assert os.path.exists(savepath)