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ExternalSessions[]

gives the list of currently active external evaluator sessions.

ExternalSessions[sys]

gives the list of sessions associated with the system sys.

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ExternalSessions   

Listing of External Evaluators »

ExternalSessions[]

gives the list of currently active external evaluator sessions.

ExternalSessions[sys]

gives the list of sessions associated with the system sys.

Details

Examples

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Basic Examples  (3)

Start a session and see it listed with ExternalSessions:

Wolfram Language code: session = StartExternalSession["NodeJS"]; ExternalSessions[]

Delete the session object:

Wolfram Language code: DeleteObject[session]

Now the session is not present in ExternalSessions:

Wolfram Language code: ExternalSessions[]

Start sessions and list them independently by specifying the system:

Wolfram Language code: py = StartExternalSession["Python"] js = StartExternalSession["NodeJS"]

ExternalSessions[sys] only shows sessions for that system:

Wolfram Language code: #["System"]& /@ ExternalSessions["Python"]
Wolfram Language code: #["System"]& /@ ExternalSessions["NodeJS"]

Delete the session objects:

Wolfram Language code: DeleteObject[{py, js}]

Start some sessions and delete all of them with DeleteObject and ExternalSessions:

Wolfram Language code: sessions = Table[StartExternalSession["Python"], $ProcessorCount]

DeleteObject works with a list of more than one ExternalSessionObject:

Wolfram Language code: DeleteObject[sessions]

Scope  (1)

Sessions are automatically removed from ExternalSessions once they are deleted:

Wolfram Language code: session = StartExternalSession["NodeJS"]; MemberQ[session]@ExternalSessions[]
Wolfram Language code: DeleteObject[session]; MemberQ[session]@ExternalSessions[]

Neat Examples  (1)

Start sessions to list all their properties:

Wolfram Language code: Table[StartExternalSession[RandomChoice[{"Python", "NodeJS"}]], $ProcessorCount];

Make a dataset of the various properties of all the sessions:

Wolfram Language code: Dataset[Function[{session}, AssociationMap[session, session["Properties"]]] /@ ExternalSessions[]]
Wolfram Research (2017), ExternalSessions, Wolfram Language function, https://reference.wolfram.com/language/ref/ExternalSessions.html (updated 2020).

Text

Wolfram Research (2017), ExternalSessions, Wolfram Language function, https://reference.wolfram.com/language/ref/ExternalSessions.html (updated 2020).

CMS

Wolfram Language. 2017. "ExternalSessions." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2020. https://reference.wolfram.com/language/ref/ExternalSessions.html.

APA

Wolfram Language. (2017). ExternalSessions. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/ExternalSessions.html

BibTeX

@misc{reference.wolfram_2026_externalsessions, author="Wolfram Research", title="{ExternalSessions}", year="2020", howpublished="\url{https://reference.wolfram.com/language/ref/ExternalSessions.html}", note=[Accessed: 12-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_externalsessions, organization={Wolfram Research}, title={ExternalSessions}, year={2020}, url={https://reference.wolfram.com/language/ref/ExternalSessions.html}, note=[Accessed: 12-June-2026]}