Source code:
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The asyncio module can be invoked as a script via python-masyncio to inspect the task graph of another running Python process without modifying it or restarting it. The asyncio.tools submodule implements this interface.
The following commands inspect the process identified by PID:
$ python-masynciopstreePID $ python-masynciopsPID The commands read the target process state without executing any code in it. They are only available on supported platforms and may require permission to inspect another process. See the
for details.
See also
Programmatic APIs for inspecting the async call graph of a task or future in the current process.
The command examples below use this program, which creates a task hierarchy suitable for inspection and prints its process ID:
example.py
importasyncioimportosasyncdefplay(track):awaitasyncio.sleep(3600)print(f"🎵 Finished: {track}")asyncdefalbum(name,tracks):asyncwithasyncio.TaskGroup()astg:fortrackintracks:tg.create_task(play(track),name=track)asyncdefmain():print(f"PID: {os.getpid()}")asyncwithasyncio.TaskGroup()astg:tg.create_task(album("Sundowning",["TNDNBTG","Levitate"]),name="Sundowning",)tg.create_task(album("TMBTE",["DYWTYLM","Aqua Regia"]),name="TMBTE",)asyncio.run(main())Run the program in one terminal and leave it running:
$ pythonexample.py PID: 12345Then pass the printed process ID to the commands from another terminal. Thread IDs, task IDs, file paths, and line numbers vary between runs and source layouts.
Added in version 3.14.
Command-line options
pstreePID
Display task and coroutine relationships as a tree. Each task is shown with its full coroutine stack, nested under the task (if any) that is awaiting it. This subcommand is useful for quickly identifying which branch of a task hierarchy is blocked and where in its coroutine stack execution has paused:
$ python-masynciopstree12345└── (T) Task-1 └── main example.py:12 └── TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:75 └── TaskGroup._aexit Lib/asyncio/taskgroups.py:124 ├── (T) Sundowning │ └── album example.py:7 │ └── TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:75 │ └── TaskGroup._aexit Lib/asyncio/taskgroups.py:124 │ ├── (T) TNDNBTG │ │ └── play example.py:4 │ │ └── sleep Lib/asyncio/tasks.py:702 │ └── (T) Levitate │ └── play example.py:4 │ └── sleep Lib/asyncio/tasks.py:702 └── (T) TMBTE └── album example.py:7 └── TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:75 └── TaskGroup._aexit Lib/asyncio/taskgroups.py:124 ├── (T) DYWTYLM │ └── play example.py:4 │ └── sleep Lib/asyncio/tasks.py:702 └── (T) Aqua Regia └── play example.py:4 └── sleep Lib/asyncio/tasks.py:702If the await graph contains a cycle, pstree reports an error instead of printing a tree. A cycle in the await graph is unusual and typically indicates a programming error:
$ python-masynciopstree12345ERROR: await-graph contains cycles - cannot print a tree!cycle: Task-2 → Task-3 → Task-2psPID
Display a flat table of all pending tasks in the process PID. Each row shows the event-loop thread ID, task ID and name, coroutine stack, and the awaiting task’s stack, name, and ID, if any.
This subcommand prints all tasks regardless of whether the await graph contains cycles:
$ python-masynciops12345tid task id task name coroutine stack awaiter chain awaiter name awaiter id------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------18445801 0x10a456060 Task-1 TaskGroup._aexit -> TaskGroup.__aexit__ -> main 0x018445801 0x10a439f60 Sundowning TaskGroup._aexit -> TaskGroup.__aexit__ -> album TaskGroup._aexit -> TaskGroup.__aexit__ -> main Task-1 0x10a45606018445801 0x10a439d70 TMBTE TaskGroup._aexit -> TaskGroup.__aexit__ -> album TaskGroup._aexit -> TaskGroup.__aexit__ -> main Task-1 0x10a45606018445801 0x10a2a3a80 TNDNBTG sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album Sundowning 0x10a439f6018445801 0x10a2a38a0 Levitate sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album Sundowning 0x10a439f6018445801 0x10a2d7150 DYWTYLM sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album TMBTE 0x10a439d7018445801 0x10a6bdaa0 Aqua Regia sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album TMBTE 0x10a439d70