REPL

Getting started

Bring the power of Jupyter kernels to your editor! The built-in REPL for Zed allows you to run code interactively in your editor similarly to a notebook with your own text files.

Installation

Zed supports running code in multiple languages. To get started, you need to install a kernel for the language you want to use.

Currently supported languages:

Once installed, you can start using the REPL in the respective language files, or other places those languages are supported, such as Markdown. If you recently added the kernels, run the repl: refresh kernelspecs command to make them available in the editor.

Using the REPL

To start the REPL, open a file with the language you want to use and use the repl: run command (defaults to ctrl-shift-enter on macOS) to run a block, selection, or line. You can also click on the REPL icon in the toolbar.

The repl: run command will be executed on your selection(s), and the result will be displayed below the selection.

Outputs can be cleared with the repl: clear outputs command, or from the REPL menu in the toolbar.

Cell mode

Zed supports notebooks as scripts using the # %% cell separator in Python and // %% in TypeScript. This allows you to write code in a single file and run it as if it were a notebook, cell by cell.

The repl: run command will run each block of code between the # %% markers as a separate cell.

# %% Cell 1
import time
import numpy as np

# %% Cell 2
import matplotlib.pyplot as plt
import matplotlib.pyplot as plt
from matplotlib import style
style.use('ggplot')

Language specific instructions

Python

Global environment

On macOS, your system Python will not work. Either set up pyenv or use a virtual environment.

To setup your current python to have an available kernel, run:

pip install ipykernel
python -m ipykernel install --user

Conda Environment

source activate myenv
conda install ipykernel
python -m ipykernel install --user --name myenv --display-name "Python (myenv)"

Virtualenv with pip

source activate myenv
pip install ipykernel
python -m ipykernel install --user --name myenv --display-name "Python (myenv)"

R (Ark Kernel)

Install Ark by downloading the release for your operating system. E.g. for macOS just unpack ark binary and put it into /usr/local/bin. Then run:

ark --install

R (Xeus Kernel)

  • Install Xeus-R
  • Install the R Extension for Zed (search for R in Zed Extensions)

Typescript: Deno

deno jupyter --install

Julia

  • Download and install Julia from the official website.
  • Install the Julia Extension for Zed (search for Julia in Zed Extensions)

Scala

  • Install Scala with cs setup (Coursier): https://www.scala-lang.org/download/
    • brew install coursier/formulas/coursier && cs setup
  • REPL (Almond) Setup Instructions https://almond.sh/docs/quick-start-install
    • brew install --cask temurin (Eclipse foundation official OpenJDK binaries)
    • brew install coursier/formulas/coursier && cs setup
    • coursier launch --use-bootstrap almond -- --install

Changing which kernel is used per language

Zed automatically detects the available kernels on your system. If you need to configure a different default kernel for a language, you can assign a kernel for any supported language in your settings.json.

{
  "jupyter": {
    "kernel_selections": {
      "python": "conda-env",
      "typescript": "deno",
      "javascript": "deno",
      "r": "ark"
    }
  }
}

Debugging Kernelspecs

Available kernels are shown via the repl: sessions command. To refresh the kernels you can run, use the repl: refresh kernelspecs command.

If you have jupyter installed, you can run jupyter kernelspec list to see the available kernels.

$ jupyter kernelspec list
Available kernels:
  ark                   /Users/z/Library/Jupyter/kernels/ark
  conda-base            /Users/z/Library/Jupyter/kernels/conda-base
  deno                  /Users/z/Library/Jupyter/kernels/deno
  python-chatlab-dev    /Users/z/Library/Jupyter/kernels/python-chatlab-dev
  python3               /Users/z/Library/Jupyter/kernels/python3
  ruby                  /Users/z/Library/Jupyter/kernels/ruby
  rust                  /Users/z/Library/Jupyter/kernels/rust

Note: Zed makes best effort usage of sys.prefix and CONDA_PREFIX to find kernels in Python environments. If you want explicitly control run python -m ipykernel install --user --name myenv --display-name "Python (myenv)" to install the kernel directly while in the environment.