DOC-4560 pipe/transaction examples (#3449)

Author: andy-stark-redis

doctests/trans_pipe.py

@@ -0,0 +1,98 @@
+# EXAMPLE: pipe_trans_tutorial
+# HIDE_START
+"""
+Code samples for vector database quickstart pages:
+    https://redis.io/docs/latest/develop/get-started/vector-database/
+"""
+# HIDE_END
+import redis
+
+# STEP_START basic_pipe
+r = redis.Redis(decode_responses=True)
+# REMOVE_START
+for i in range(5):
+    r.delete(f"seat:{i}")
+
+r.delete("shellpath")
+# REMOVE_END
+
+pipe = r.pipeline()
+
+for i in range(5):
+    pipe.set(f"seat:{i}", f"#{i}")
+
+set_5_result = pipe.execute()
+print(set_5_result)  # >>> [True, True, True, True, True]
+
+pipe = r.pipeline()
+
+# "Chain" pipeline commands together.
+get_3_result = pipe.get("seat:0").get("seat:3").get("seat:4").execute()
+print(get_3_result)  # >>> ['#0', '#3', '#4']
+# STEP_END
+# REMOVE_START
+assert set_5_result == [True, True, True, True, True]
+assert get_3_result == ['#0', '#3', '#4']
+# REMOVE_END
+
+# STEP_START trans_watch
+r.set("shellpath", "/usr/syscmds/")
+
+with r.pipeline() as pipe:
+    # Repeat until successful.
+    while True:
+        try:
+            # Watch the key we are about to change.
+            pipe.watch("shellpath")
+
+            # The pipeline executes commands directly (instead of
+            # buffering them) from immediately after the `watch()`
+            # call until we begin the transaction.
+            current_path = pipe.get("shellpath")
+            new_path = current_path + ":/usr/mycmds/"
+
+            # Start the transaction, which will enable buffering
+            # again for the remaining commands.
+            pipe.multi()
+
+            pipe.set("shellpath", new_path)
+
+            pipe.execute()
+
+            # The transaction succeeded, so break out of the loop.
+            break
+        except redis.WatchError:
+            # The transaction failed, so continue with the next attempt.
+            continue
+
+get_path_result = r.get("shellpath")
+print(get_path_result)  # >>> '/usr/syscmds/:/usr/mycmds/'
+# STEP_END
+# REMOVE_START
+assert get_path_result == '/usr/syscmds/:/usr/mycmds/'
+r.delete("shellpath")
+# REMOVE_END
+
+# STEP_START watch_conv_method
+r.set("shellpath", "/usr/syscmds/")
+
+
+def watched_sequence(pipe):
+    current_path = pipe.get("shellpath")
+    new_path = current_path + ":/usr/mycmds/"
+
+    pipe.multi()
+
+    pipe.set("shellpath", new_path)
+
+
+trans_result = r.transaction(watched_sequence, "shellpath")
+print(trans_result)  # True
+
+get_path_result = r.get("shellpath")
+print(get_path_result)  # >>> '/usr/syscmds/:/usr/mycmds/'
+# REMOVE_START
+assert trans_result
+assert get_path_result == '/usr/syscmds/:/usr/mycmds/'
+# REMOVE_END
+# STEP_END