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✓ Uses Rust 2018 edition

0.5.1 Apr 16, 2020
0.5.0 Jan 21, 2020
0.4.7 Dec 15, 2019
0.4.5 Sep 13, 2019
0.2.0 Oct 8, 2018

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EvCxR Jupyter Kernel

Latest Version

A Jupyter Kernel for the Rust programming language.


Linux (Debian/Ubuntu)

sudo apt install jupyter-notebook
cargo install evcxr_jupyter
evcxr_jupyter --install

Alternative instructions if you want to use libzmq from your system:

sudo apt install libzmq3-dev jupyter-notebook
cargo install evcxr_jupyter --no-default-features
evcxr_jupyter --install

Once installed, you should be able to start Juypter notebook with:


Once it starts, it should open a new tab in your browser, or at least print a link for you to open. From this tab you can select File -> New Notebook -> Rust.

Mac OS X

  • Install jupyter or jupyterlab (eg. via anaconda)
  • Install cmake. These instructions might help.
cargo install evcxr_jupyter
evcxr_jupyter --install

Alternative instructions if you want to use libzmq from your system. Note, if following these instructions, then you shouldn't need to install cmake.

brew install zeromq pkg-config
cargo install evcxr_jupyter --no-default-features
evcxr_jupyter --install


Note that Evcxr on Windows appears to be substantially slower than on other platforms. We're not yet sure why.

  • Install jupyter or jupyterlab (eg. via anaconda)
  • Install CMake
cargo install evcxr_jupyter
evcxr_jupyter --install

If you'd like to install ZMQ yourself, rather than having cargo install build it for you, then These instructions might help.

Usage notes

  • To see what variables you've got defined, type ":vars".
  • Don't ask Jupyter to "interrupt kernel", it won't work. Rust threads can't be interrupted.
  • If your code panics, all variables will be lost. You can optionally run :preserve_vars_on_panic 1 to turn on preservation of variables. However note that this will slow down compilation. Also, only variables that either are not referenced by the code being run, or are Copy will be preserved.
  • If your code segfaults (e.g. due to buggy unsafe code), aborts, exits etc, the process in which the code runs will be restarted. All variables will be lost.

Custom output

The last expression in a cell gets printed. By default, we'll use the debug formatter to emit plain text. If you'd like, you can provide a function to show your type (or someone else's type) as HTML (or an image). To do this, the type needs to implement a method called evcxr_display which should then print one or more mime-typed blocks to stdout. Each block starts with a line containing BEGIN_EVCXR_OUTPUT followed by the mime type, then a newline, the content then ends with a line containing EVCXR_END_CONTENT.

For example, the following shows how you might provide a custom display function for a type Matrix. You can copy this code into a Jupyter notebook cell to try it out.

use std::fmt::Debug;
pub struct Matrix<T> {pub values: Vec<T>, pub row_size: usize}
impl<T: Debug> Matrix<T> {
    pub fn evcxr_display(&self) {
        let mut html = String::new();
        for r in 0..(self.values.len() / self.row_size) {
            for c in 0..self.row_size {
                html.push_str(&format!("{:?}", self.values[r * self.row_size + c]));
        println!("EVCXR_BEGIN_CONTENT text/html\n{}\nEVCXR_END_CONTENT", html);
let m = Matrix {values: vec![1,2,3,4,5,6,7,8,9], row_size: 3};

It's probably a good idea to either print the whole block at once, or to lock stdout then print the block. This should ensure that nothing else prints to stdout at the same time (at least no other Rust code).

If the content is binary (e.g. mime type "image/png") then it should be base64 encoded.

Startup options

If you always want particular options set, you can add these to init.evcxr which, if present will be run on startup. Sample locations:

  • Linux: ~/.config/evcxr/init.evcxr
  • Mac: /Users/Alice/Library/Preferences/evcxr/init.evcxr
  • Windows: C:\Users\Alice\AppData\Roaming\evcxr\init.evcxr

For example, if you want to always turn on optimization (will make stuff slower to compile), you might put the following in init.evcxr:

:opt 2

sccache integration

sccache caches compilation outputs. If you frequently use the same crates, this can speed things up quite a bit.

  • cargo install sccache
  • Add :sccache 1 to your init.evcxr (see Startup options above).
  • See sccache for more details about sccache.

Using lld for linking

The linker "lld" will be used automatically if detected, except on Mac OS, where it doesn't work. Installing it is recommended, since it's generally a good bit faster than the system linker. On Debian-based systems you might be able to install it with:

sudo apt install lld

You can check if it's being used when within evcxr by running :linker.

Installing from git head

If there's a bugfix in git that you'd like to try out, you can install directly from git with the command:

cargo install --force --git https://github.com/google/evcxr.git evcxr_jupyter


evcxr_jupyter --uninstall
cargo uninstall evcxr_jupyter


~115K SLoC