Interpreter Startup

First run

When Positron starts for the first time in a new workspace, it will start a Python and/or R interpreter session based on your workspace characteristics and whether there is evidence of RStudio being used recently.

Typically when starting Python or R without other clues about which version to start, Positron will start the most recent version of the interpreter (e.g. if you have R 4.2 and R 4.3 installed, it’ll start R 4.3).

If you are an R user, see the R discovery guide for more information on available installations.

RStudio detection

Positron tries to start R for R users and Python for Python users by checking to see if RStudio is installed and has been recently used. The latter check is done by looking in ~/.local/share/rstudio for files written less than a month ago. If you do not want Positron to consider you an RStudio user, remove this folder or rename it.

Subsequent runs

When Positron starts in a workspace that has been used before, it will start the same language interpreter that was running the last time you used the workspace.

In the case of R, there is some additional subtlety: When Positron records which R version was most recently used in a workspace, it also notes whether that R version is the system’s default R version. In subsequent runs, Positron will launch the system’s default R version, even if that is a different version number from the last-used R version. We believe this behaviour is the least surprising for most users. If you want to use a specific, non-default R version in a workspace, select it explicitly once and it will be launched in future runs.

If Positron starts an interpreter you don’t need, just delete the session, and it will stop starting automatically in that workspace.

Implicit startup

In addition to starting up an interpreter session when the workspace is first opened, Positron will also automatically start an interpreter session when it looks like one is needed. For example, a Python session will start:

• When you open a .py file
• When you execute Python code

Configuring interpreter startup

If the interpreter that Positron uses by default isn’t a good fit, you can customize and configure how interpreter sessions are started using the interpreters.startupBehavior settings.

Per-language interpreter startup behavior

In the Settings UI, search for @lang:r interpreters.startupBehavior or @lang:python interpreters.startupBehavior, and choose the desired configuration. The selected startup behavior will be applied to the corresponding language.

For example, if you only ever use Python and never want R to start, set @lang:r interpreters.startupBehavior to "disabled" to hide R interpreters from the Positron UI altogether. You can specify this at either the user or workspace level, and your configuration will appear in your settings.json as:

{
    "[r]": {
        "interpreters.startupBehavior": "disabled"
    }
}

Alternatively, if you are mainly an R user, but occasionally use Python, you can set @lang:python interpreters.startupBehavior to "manual" to prevent Python interpreter sessions from starting automatically. This still allows you to start a Python interpreter session manually:

{
    "[python]": {
        "interpreters.startupBehavior": "manual"
    }
}

General interpreter startup behavior

In the Settings UI, find the interpreters.startupBehavior setting without a language key, and choose the desired configuration. The selected startup behavior will be applied to all interpreters.

Note that if any per-language startup behavior is set, it takes precedence over the general interpreter startup behavior setting.