Mon, Jan 23, 2017Infinite Loops
At Repl.it we aim to make the full power of programming easily accessible for everyone. That's why when we designed our code execution service we decided that we would not timebox users' programs or sessions. [](preview end) This was a great design decision because it allowed people to build complex programs, things like infinite looping animations, and games -- like this fun text-based game: But this also meant you could hit infinite loops. And in most cases this was okay because you can hit stop and we'd kill the program for you. Except this failed in two cases: If the program was sending so much output data to your browser that it was causing it lock up.
- Thu, Jan 19, 2017
Reorder Assignments with Teams for Education
At Repl.it our mission is to make programming more accessible, and the best way we found to achieve this is to support, you, the teachers on the ground doing working with students. That's why we want to make sure you control the student experience and today we're making it possible to control the assignments order from your classroom dashboard.[](preview end) We're giving you seven different sorting options: Alphabetic (both a-z and z-a), Publish date (both old-new and new-old), Due date (both sooner-later and later-sooner) and finally, Manual where you'll be able to drag and drop assignments in any order. Additionally, we're unifying the teacher’s and the student’s classroom dashboard by allowing you to choose any reordering option. That means both sides will see the same assignments order on their classroom dashboard which avoids any kind of confusion between the teacher and the students. To remove any friction at the students' end we're removing the sorting options in the student dashboard. Students will receive the order that their teacher chose for them; and soon this will allow teachers to add assignment dependencies which will require students to complete their assignment before moving to the next one. And as always, here is a gif of how it looks like:
- Fri, Dec 23, 2016
Live File Updates
Today we're excited to release a feature which shows any files your program creates directly inside the REPL. And any time that file changes it will be updated live in the editor. This can be anything from a text file to a gif. We also added support for matplotlib in python3 so you can make pretty graphs and watch them update live. Like this: And we don't stop you from rewriting your own source file so you can write a program which modifies itself, like this counting quine.
- Fri, Dec 2, 2016
Python Package Search
We recently made it possible to import any package from PyPi. However, people who missed the announcement didn't know this was possible. There was also no good way to search and explore packages. That's why today we're excited to introduce a package search widget. You'll be able to search for any python package without leaving the programming environment.
- Mon, Nov 28, 2016
Introducing Step Debugging for Python
Debug your Python3 programs from your browser At Repl.it, our goal is to make programming more accessible, and as part of this we aim to provide the full power of popular programming environments with no setup time. And I don't think it's an understatement to say that debugging is the majority of what we, as programmers, do. [](preview end) That's why today we're making it possible to step-debug through your Python 3 code right from the browser. We've built a new debug pane that makes it easy step in, out, over, and resume your code. All the common operations a typical debugger would do. To get started:
- Mon, Nov 14, 2016
Learning Devops & AWS on the Job: Building and Scaling a Service
Or, what I wish you I knew before building Repl.it's code execution service new drinking game "name that AWS service logo" — TJ Holowaychuk (@tjholowaychuk) March 23, 2016 I, by no means, identify as a devops or even a backend engineer. Most of my professional experience has been equally split between frontend/product and developer tooling. I also primarily learn by doing and bias towards simplicity and MVPs -- almost to a fault. So when I approached building a service on AWS I took a very simple path and increased complexity as the service scaled up. Here are all the steps that I went through before getting to something that I'm not totally ashamed of. eval.repl.it
- Sat, Nov 12, 2016
Introducing Pylint Support
Today, we're excited to introduce lint support for Python3. Where previously you had to run your code, look at the console for an error, find the line number of the error and then find that line in your editor. Now, we'll show you errors and potential mistakes live as you type! This is powered by pylint, so in addition to obvious errors like syntax errors, pylint will point out potential programmer mistakes like unused variables, redefnining builtins and many more!
- Tue, Oct 25, 2016
from PyPi import *
Import any Python Package At Repl.it, our goal is to make programming more accessible, and as part of this we aim to provide the full power of popular programming environments with no setup time. And no modern programming language is complete without third-party packages. [](preview end) That's why today we're making every Python package ever immediately available on repl.it. Just select the language (Python or Python3) and start importing packages: You can explore Python packages here.
- Tue, Oct 4, 2016
Introducing Turtle Graphics For Python
Ever since the LOGO programming language educators have been using Turtle Graphics to demonstrate the power of programming to their students while making it fun and interesting.[](preview end) In fact, my first real programming experience was when I was 6 years old learning LOGO at school. I learned how to program the turtle to draw a square and a triangle which I then put together to create a house. However, I was frustrated that I had to keep repeating the code to create a village made from multiple houses -- and that's how discovered loops! It's a natural way for children to learn programming. Here is an example turtle graphic house in repl.it :) So far, we've been focused on what we think was largely missing from the web: running programs that typically require installing a compiler or an interpreter on your computer. However, now that we've built tools for teachers to bring programming to their classroom, many want to use turtle graphics as part of their cirriculum. And that's why we're excited to introduce Turtle Graphics support for Python. To get started just select Python (with Turtle) from the list of languages, import the turtle module and start drawing!
- Wed, Sep 28, 2016
Scheduled Assignments
Today, we're introducing scheduled assignments. Teachers using Repl.it Classroom can now schedule assignments to be published in the future. You can imagine working on your assignment, schedule a publish date, go on vacation, and still have your students receive their assignments at the right time.[](preview end) When the assignment is finally published your students will receive a notification informing them of it. You can get to this menu from the second page in the assignment creation flow. As always, feel free to reach out at [email protected] with feedback. We'd love to hear about how this feature helped you. Or, more importantly, if there is something we can be doing better.
- Thu, Jul 28, 2016
Vagueness to Clarity
Simple design is not only how the product looks like, but more importantly, how the product functions; it’s about creating the easiest and simplest path for the user to accomplish their goal. Usually, simple design comes from complex requirements and a lot of ideas — in order to break it down I usually go through a process that I call Vagueness to Clarity[](preview end). This process requires a deep understanding of the problem to come up with the best possible solution. Most people don’t pay attention to simple products because it feels so right and intuitive when using them — it could be so frictionless to the point that nothing gets in the way of accomplishing the main goal. But simplicity is hard — it maybe counterintuitive that the cleaner the interface, the more thoughts were put into it, and the longer it went through the Vagueness to Clarity process. From vague to complex
- Thu, Jul 21, 2016
Every Project Should Have Its Own REPL
It's no secret we're big fans of REPLs. We believe that immediate access to the programming environment accelerates learning and is generally more productive. REPLs cut out the middleman -- no need to build UIs or scripts for every possible action you might want to take -- just talk to the interpreter directly.[](preview end) In every medium-to-large project we embark on we include a repl.sh script that starts out a REPL in the context of the project. This includes preloaded libraries, custom commands, and a database connection when it makes sense. You can interact with the database, use utility functions, and inspect the environment in whatever way you find useful. This is especially easy in NodeJS; the module that makes up the REPL that ships with it is made into a stand-alone module repl. Once you require('repl') you'll be able to supply it with a custom eval function which you can then use to process the and parse the code in whatever way you find useful before calling a callback with a return value. We love using async/await so we process top-level awaits with babel in the REPL to make it very easy to add, update, or delete from the development database. In the above gif you can see how we can test and iterate on our notifications page by creating notifications from the REPL and see it update instantly!
- Wed, Jun 29, 2016
View Student Performance with Classroom Overview
Before we decided to build repl.it classroom, we paid a visit to one of the schools using us in the classroom. I felt excited and anxious at the same time; I was introduced to the teacher and students in the class, and then my job started as designer observing and paying attention to every single detail.[](preview end) The teacher explained the workflow and had two students assisting her to check on the students. Seeing the teacher and student’s frustration made me see a problem, I noticed that most of the students were trying to communicate their frustrations, but they were either embarrassed or too shy. Others gave up too soon, without even trying. The two assistants solution might have been a good idea, but for students knowing the fact that they’re being watched or might be judged made them hesitant to ask for help. Towards the end of the class I was handed a piece of paper and was asked to list the student names who completed the assignment successfully. A teacher should be able to see where her students are at—to have bird’s-eye view for the classroom so attention can be paid for the ones who need it the most, plus it would be good way to track progress. Hovering around each student individually can be time and energy consuming. Introducing Classroom Overview The Student Overview is a feature of the teacher dashboard that we’re introducing. Where previously you had to go into each assignment to see the progress for each student individually (which ironically mirrors the physical classroom experience described above). The teacher classroom dashboard is now divided into assignment and student sections. The assignments section lists out the assignments published or in draft and allows you to create a new assignment. The student section is all about the students, their names, completion percentages for all their assignments and the current submission status.
- Sun, Jun 26, 2016
Distributed Websocket Rate Limiting
Rate limiting is standard practice for services offering an API. It's used for both protecting against bad actors, for example, attempting DOS attacks and to simply enforce limits on the service. There are many resources on the web on how to implement a rate limiter in your favorite language/stack. However, I couldn't find anything on how to rate limit Websocket connections (they differ in that they are persistent connections).[](preview end) If you're implementing an HTTP API rate limiter and your service endpoint is a single server then it's pretty simple -- you keep an in-memory variable that you increment. Things get trickier, however, when you're serving requests from multiple servers. That's when you start needing a central shared "state". For this, most developers use Redis. In fact, the rate limiting use case is so prevalent in Redis that it gets a mention on the docs for the INCR function: The requirement here is to limit calls to 10 calls per second per IP address. So a key is constructed by concatenating the user's IP address with the current timestamp. This is then incremented with every call and checked to make sure they haven't exceeded the limit. Simple enough (you can also implement this using your favorite language and Redis library). In our case, our code execution API gives our customers and users an HTTP and a Websocket interface. The reason you'd need a persistent connection is to build a stateful interpreter/REPL. But persistent connections costs us system resources because we need to start a container and an interpreter/compiler process that waits for the next command to execute. For this reason we have to enforce a limit on concurrent open connections. The challenge with this is implementing it for a distributed service (we serve our users from different servers with no centralized server managing state). As we've seen above, Redis is the go-to technology to solve this problem. However, our use case differs in that we don't limit calls for a certain time interval, instead our limit is one the total number of open connections at any given time. The first solution that came to mind:
- Fri, Jun 24, 2016
API Docs
[Update Oct 2022: We have retired our API, we are excited by our previous work but we do not have the resources to support this at the moment.] Repl.it's code execution API is an HTTP and WebSocket endpoint that you connect to and send code to execute. You can connect from any device or browser and start executing code. This guide will describe the concepts behind the service, how it can be used, and provide a step-by-step guide for signing up and trying out the service! Code Execution You're probably here because you want to run some user code in an app or website somewhere. Our customers use the Repl.it API for many different things including: In-browser coding environments In-browser coding exercises