1# REPL
2
3## Getting started
4
5Bring the power of [Jupyter kernels](https://docs.jupyter.org/en/latest/projects/kernels.html) 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.
6
7<figure style="overflow: hidden; border-top-left-radius: 2px; border-top-right-radius: 2px;">
8 <video loop controls playsinline>
9 <source
10 src="https://customer-snccc0j9v3kfzkif.cloudflarestream.com/aec66e79f23d6d1a0bee5e388a3f17cc/downloads/default.mp4"
11 type='video/webm; codecs="vp8.0, vorbis"'
12 />
13 <source
14 src="https://customer-snccc0j9v3kfzkif.cloudflarestream.com/aec66e79f23d6d1a0bee5e388a3f17cc/downloads/default.mp4"
15 type='video/mp4; codecs="avc1.4D401E, mp4a.40.2"'
16 />
17 <source
18 src="https://zed.dev/img/post/repl/typescript-deno-kernel-markdown.png"
19 type="image/png"
20 />
21 </video>
22</figure>
23
24## Installation
25
26Zed supports running code in multiple languages. To get started, you need to install a kernel for the language you want to use.
27
28**Currently supported languages:**
29
30- [Python (ipykernel)](#python)
31- [R (Ark)](#r)
32- [TypeScript (Deno)](#typescript-deno)
33
34Once 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.
35
36## Using the REPL
37
38To 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.
39
40The `repl: run` command will be executed on your selection(s), and the result will be displayed below the selection.
41
42Outputs can be cleared with the `repl: clear outputs` command, or from the REPL menu in the toolbar.
43
44### Cell mode
45
46Zed supports [notebooks as scripts](https://jupytext.readthedocs.io/en/latest/formats-scripts.html) 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.
47
48The `repl: run` command will run each block of code between the `# %%` markers as a separate cell.
49
50```python
51# %% Cell 1
52import time
53import numpy as np
54
55# %% Cell 2
56import matplotlib.pyplot as plt
57import matplotlib.pyplot as plt
58from matplotlib import style
59style.use('ggplot')
60```
61
62## Language specific instructions
63
64### Python {#python}
65
66#### Global environment
67
68<div class="warning">
69
70On MacOS, your system Python will _not_ work. Either set up [pyenv](https://github.com/pyenv/pyenv?tab=readme-ov-file#installation) or use a virtual environment.
71
72</div>
73
74To setup your current python to have an available kernel, run:
75
76```
77pip install ipykernel
78python -m ipykernel install --user
79```
80
81#### Conda Environment
82
83```
84source activate myenv
85conda install ipykernel
86python -m ipykernel install --user --name myenv --display-name "Python (myenv)"
87```
88
89#### Virtualenv with pip
90
91```
92source activate myenv
93pip install ipykernel
94python -m ipykernel install --user --name myenv --display-name "Python (myenv)"
95```
96
97### R
98
99Install [Ark](https://github.com/posit-dev/ark/releases) 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:
100
101```
102ark --install
103```
104
105### Typescript: Deno {#typescript-deno}
106
107[Install Deno](https://docs.deno.com/runtime/manual/getting_started/installation/) and then install the Deno jupyter kernel:
108
109```
110deno jupyter --install
111```
112
113### Other languages
114
115The following languages and kernels are also supported. You can help us out by expanding their installation instructions and configuration:
116
117- [Julia (IJulia)](https://github.com/JuliaLang/IJulia.jl)
118- R
119 - [Ark Kernel](https://github.com/posit-dev/ark) - via Positron, formerly RStudio
120 - [Xeus-R](https://github.com/jupyter-xeus/xeus-r)
121- [Scala (almond)](https://almond.sh/docs/quick-start-install)
122
123## Changing which kernel is used per language {#changing-kernels}
124
125Zed automatically detects the available kernels on your system. If you need to configure a different default kernel for a
126language, you can assign a kernel for any supported language in your `settings.json`.
127
128```json
129{
130 "jupyter": {
131 "kernel_selections": {
132 "python": "conda-env",
133 "typescript": "deno",
134 "javascript": "deno",
135 "r": "ark"
136 }
137 }
138}
139```
140
141## Debugging Kernelspecs
142
143Available kernels are shown via the `repl: sessions` command. To refresh the kernels you can run, use the `repl: refresh kernelspecs` command.
144
145If you have `jupyter` installed, you can run `jupyter kernelspec list` to see the available kernels.
146
147```
148$ jupyter kernelspec list
149Available kernels:
150 ark /Users/z/Library/Jupyter/kernels/ark
151 conda-base /Users/z/Library/Jupyter/kernels/conda-base
152 deno /Users/z/Library/Jupyter/kernels/deno
153 python-chatlab-dev /Users/z/Library/Jupyter/kernels/python-chatlab-dev
154 python3 /Users/z/Library/Jupyter/kernels/python3
155 ruby /Users/z/Library/Jupyter/kernels/ruby
156 rust /Users/z/Library/Jupyter/kernels/rust
157```
158
159Note: 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.