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diff --git a/examples/prompts/auto-completion/slow-completions.py b/examples/prompts/auto-completion/slow-completions.py
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+++ b/examples/prompts/auto-completion/slow-completions.py
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+#!/usr/bin/env python
+"""
+An example of how to deal with slow auto completion code.
+
+- Running the completions in a thread is possible by wrapping the
+  `Completer` object in a `ThreadedCompleter`. This makes sure that the
+  ``get_completions`` generator is executed in a background thread.
+
+  For the `prompt` shortcut, we don't have to wrap the completer ourselves.
+  Passing `complete_in_thread=True` is sufficient.
+
+- We also set a `loading` boolean in the completer function to keep track of
+  when the completer is running, and display this in the toolbar.
+"""
+import time
+
+from prompt_toolkit.completion import Completer, Completion
+from prompt_toolkit.shortcuts import CompleteStyle, prompt
+
+WORDS = [
+    "alligator",
+    "ant",
+    "ape",
+    "bat",
+    "bear",
+    "beaver",
+    "bee",
+    "bison",
+    "butterfly",
+    "cat",
+    "chicken",
+    "crocodile",
+    "dinosaur",
+    "dog",
+    "dolphin",
+    "dove",
+    "duck",
+    "eagle",
+    "elephant",
+    "fish",
+    "goat",
+    "gorilla",
+    "kangaroo",
+    "leopard",
+    "lion",
+    "mouse",
+    "rabbit",
+    "rat",
+    "snake",
+    "spider",
+    "turkey",
+    "turtle",
+]
+
+
+class SlowCompleter(Completer):
+    """
+    This is a completer that's very slow.
+    """
+
+    def __init__(self):
+        self.loading = 0
+
+    def get_completions(self, document, complete_event):
+        # Keep count of how many completion generators are running.
+        self.loading += 1
+        word_before_cursor = document.get_word_before_cursor()
+
+        try:
+            for word in WORDS:
+                if word.startswith(word_before_cursor):
+                    time.sleep(0.2)  # Simulate slowness.
+                    yield Completion(word, -len(word_before_cursor))
+
+        finally:
+            # We use try/finally because this generator can be closed if the
+            # input text changes before all completions are generated.
+            self.loading -= 1
+
+
+def main():
+    # We wrap it in a ThreadedCompleter, to make sure it runs in a different
+    # thread. That way, we don't block the UI while running the completions.
+    slow_completer = SlowCompleter()
+
+    # Add a bottom toolbar that display when completions are loading.
+    def bottom_toolbar():
+        return " Loading completions... " if slow_completer.loading > 0 else ""
+
+    # Display prompt.
+    text = prompt(
+        "Give some animals: ",
+        completer=slow_completer,
+        complete_in_thread=True,
+        complete_while_typing=True,
+        bottom_toolbar=bottom_toolbar,
+        complete_style=CompleteStyle.MULTI_COLUMN,
+    )
+    print("You said: %s" % text)
+
+
+if __name__ == "__main__":
+    main()