RUSTPYTHONPATH is not set when using Settings::default() without clap

Summary

I've manually set the RUSTPYTHONPATH in the system environment variable, Rust sees the correct folder location prior to calling the
vm::Interpreter::without_stdlib(Default::default()).enter(|vm| { ..

and yet, the following error appears:

encodings initialization failed. Only utf-8 encoding will be supported.
ModuleNotFoundError: No module named 'encodings'

The above exception was the direct cause of the following exception:

RuntimeError: Could not import encodings. Is your RUSTPYTHONPATH set? If you don't have access to a consistent external environment (e.g. if you're embedding rustpython in another application), try enabling the freeze-stdlib feature

Expected

No message

Actual

encodings initialization failed. Only utf-8 encoding will be supported.
ModuleNotFoundError: No module named 'encodings'

The above exception was the direct cause of the following exception:

RuntimeError: Could not import encodings. Is your RUSTPYTHONPATH set? If you don't have access to a consistent external environment (e.g. if you're embedding rustpython in another application), try enabling the freeze-stdlib feature

Python Documentation

Does the problem persist after running cargo clean?

Yes, it does

If it's helpful, the dependencies tree is:

rustpython = { git="https://github.com/RustPython/RustPython", features = ['jit']}

You probably need to depend on the rustpython-vm crate.

Aren't the crates yanked? 3+ years old...

Try this:

rustpython-vm = { git = "https://github.com/RustPython/RustPython", features = ['jit'] }

@youknowone

@youknowone Does this have anything to do with the parser migration?

The -vm is in the same git repo, so it didn't change anything adding it as a dependency. Cargo didn't even compile anythimg differently.

…

On Wed, 24 May 2023, 00:06 fanninpm, ***@***.***> wrote: Try this: rustpython-vm = { git = "https://github.com/RustPython/RustPython", features = ['jit'] } — Reply to this email directly, view it on GitHub <#4988 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ANAKPNRYGKVQZOQCEQUZHDTXHTN7JANCNFSM6AAAAAAYMA4DIQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

One last troubleshooting step: does the problem persist after deleting Cargo.lock?

@euanmacinnes

@euanmacinnes Are you using rustpython as dependency of your project? or directly using RustPython repository?

The -vm is in the same git repo,

I think using RustPython repository by that part. Then Cargo.lock will not help.

It's a dependency, as I'm looking to embed dynamically generated python functions into Rust.

…

On Wed, 24 May 2023, 14:55 Jeong, YunWon, ***@***.***> wrote: @euanmacinnes <https://github.com/euanmacinnes> Are you using rustpython as dependency of your project? or directly using RustPython repository? — Reply to this email directly, view it on GitHub <#4988 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ANAKPNRXHWGNQR2KOYFQ2HDXHWWEJANCNFSM6AAAAAAYMA4DIQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>

Oh, wow. It was totally broken for Setting::default().
RUSTPYTOHNPATH is only loaded when opts_with_clap is used.

@euanmacinnes

Hmm.. the behavior seems reasonable. It doesn't automatically load PYTHONPATH when user doesn't want.
But the the message seems very confusing.

@euanmacinnes try this:

let mut settings = Settings::default();
settings.path_list.push(<the path  you want to put>);
vm::Interpreter::without_stdlib(settings).enter(|vm| { ..

Ok nice! That works! Thanks!

2 tasks are expected to resolve this problem.

Fix error message to add path to settings.path_list and suggest RUSTPYTHONPATH as one of the way to set it when running interpreter binary.
- It can be even better by checking settings.path_list contains PYTHONPATH or RUSTPYTHONPATH and generate different message. (optional)
Add fn with_path(self, path: ...) -> Self to Settings for convenience method.

Both tasks will be easy tasks.

Is this still a problem?

fix: improve error message when RUSTPYTHONPATH not loaded in Settings

Settings::default() still leaves path_list empty on purpose, so a process-level RUSTPYTHONPATH is not applied to an embedded Interpreter::without_stdlib. That is the intended embed API.

The two follow-ups listed on this issue are in tree:

Settings::with_path (crates/vm/src/vm/setting.rs)
encodings-import failure text now says when the env var is set but was not copied into Settings / PyConfig::paths::module_search_paths, and tells embedders to build a custom Settings

Closing as resolved.

— commented by Grok 4.6

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RUSTPYTHONPATH is not set when using `Settings::default()` without clap #4988

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RUSTPYTHONPATH is not set when using Settings::default() without clap #4988

Description

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Expected

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Python Documentation

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fanninpm commented on May 23, 2023

euanmacinnes commented on May 23, 2023

euanmacinnes commented on May 23, 2023

fanninpm commented on May 23, 2023

euanmacinnes commented on May 23, 2023

fanninpm commented on May 23, 2023

fanninpm commented on May 23, 2023

euanmacinnes commented on May 24, 2023

fanninpm commented on May 24, 2023

youknowone commented on May 24, 2023

youknowone commented on May 24, 2023

euanmacinnes commented on May 24, 2023

youknowone commented on May 24, 2023

youknowone commented on May 24, 2023

euanmacinnes commented on May 29, 2023

youknowone commented on Jun 1, 2023

hbina commented on Feb 15, 2025

youknowone commented on Oct 6, 2026

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RUSTPYTHONPATH is not set when using `Settings::default()` without clap #4988