Hello friends!
Welcome to this week’s Sloth Bytes. I hope you had an amazing week!
You don't remember that meeting. Nobody does.
I bet right now you couldn't tell me what your last meeting or lecture was about even if your life depended on it.
Don't worry, I can't either. I have the memory of a goldfish. That's why I started using Granola.
It picks up your meetings automatically and transcribes everything in the background while you take notes like normal. No bot joining your call, no “recording in progress” sound, nobody knows it's there.
After the meeting, it takes your messy notes and the full transcript and turns it into a clear summary of the meeting and what you actually need to do next.
You can even share that summary with your team because I bet they forgot too.
Now nobody has to pretend they remember.
Docker For Dummies
You’ve probably heard the classic joke: "It works on my machine."
Well that joke exists for a reason.
There’s lots of situations where code literally only works on your machine for some reason.
And I guess it happened enough to where a solution was needed. That solution was Docker.
What Even Is Docker?
Docker is a tool that lets you package up your application.
Your code
Your dependencies
Your config
Everything your app needs. It gets packaged into a single portable unit called a container.
You run it on your laptop, It works. Run it on a school computer, it works. Run it on a pregnancy test, it works.
Think of it like this:
Your app is a piece of IKEA furniture and Docker is the box it comes in. Every single part is in there. The instructions. The weird annoying hex key. All of it. Wherever you take that box, you can build the same thing.
Containers vs Virtual Machines
Some of you probably noticed that containers sounds similar to a VM.
Well…
You’re a nerd
You’re correct
Containers are similar to VMs, but there are small differences that trip people up every time, so let's quickly go over it.
A VM emulates an entire computer. This means it emulates its own operating system, its own hardware, everything. It's heavy, slow to start, and eats RAM like it's not $1000 (Thanks AI).
A container is different. It doesn’t emulate everything, instead they share the host machine's operating system kernel.
Without getting too technical and nerdy, a container creates it’s own room in your machine. That room is completely isolated. It has its own files, its own processes, but it’s sharing your machine's actual CPU and memory.
A VM is like renting a whole apartment. A container is just getting your own bedroom.
This means containers are faster and lighter than VMs.
Parts of each. Small differences.
The Key Concepts
There are really only three things you need to understand about Docker:
1. The Dockerfile
Think of a dockerfile like a recipe. It contains instructions that tells Docker how to build your app.
# Start from an official Python base image
FROM python:3.11-slim
# Set working directory inside container
WORKDIR /app
# Copy your requirements and install them
COPY requirements.txt .
RUN pip install -r requirements.txt
# Copy the rest of your code
COPY . .
# What runs when the container starts
CMD ["python", "app.py"]2. The Image
When you build a Dockerfile, you get an image. An image is a frozen snapshot of your app and everything it needs. You can think of it like a class in OOP, it's the blueprint of a container.
docker build -t my-app .3. Container
A container is a running instance of an image. If an image is the class, a container is the object. It’s the actual thing.
docker run my-appThese are the 3 steps you need to “dockerize” your app:
Write the dockerfile
Build it
Run it
Pretty simple and useful.
You can spin up 10 containers from the same image. They all run the same app, totally isolated from each other.
Docker Compose
We only covered a baby example, so let’s get a bit more practical.
Real apps have multiple pieces. Could be a front-end, back-end, and database.
Now technically, you could put all those pieces into one giant docker container, but I wouldn’t recommend that and Docker doesn’t either.
Why? Because it defeats the whole point. If your database crashes, it takes your entire app down with it. If you need to scale your back-end, you'd have to scale the database too even if it didn't need it.
Each piece has a different job, so you should instead put each piece into it’s own container.
But managing three separate containers gets annoying fast.
This is why we have Docker Compose.
Docker Compose lets you define all of them in one file and spin them up together.
# docker-compose.yml
services:
frontend:
build: ./frontend # Location of that dockerfile
ports:
- "3000:3000"
backend:
build: ./backend # Location of that dockerfile
ports:
- "8000:8000"
depends_on:
- db
db: # We don't use a dockerfile for this, so we have to build it!
image: postgres:15
environment:
POSTGRES_PASSWORD: secretAnd all it takes is one command to run everything:
docker compose upThat’s it. All 3 parts of your app are fully configured and running together. You don’t have to do anything else, it’s beautiful.
When Should You Use Docker?
Yes, use it when:
You're sharing code with a team
You're deploying to a server or the cloud
Your app has specific dependency versions that need to be consistent
You're tired of "works on my machine" ruining your life
You want to self-host
Probably skip it when:
It's a tiny personal script you'll only ever run yourself
You're just learning the basics of programming (don't add this complexity early)
Your team has zero DevOps knowledge and no time to learn (Docker gets complicated fast)
Why Devs Love It
Once you “Dockerize” your app, onboarding a new developer goes from hours of installing dependencies, running build commands and crying to only running docker compose up and getting a coffee while it builds.
Fun fact: Docker was released in 2013 and became so popular that it changed how most of the software industry thinks about deployment. Kubernetes a tool that orchestrates thousands of containers was built partly because Docker made containers so mainstream that companies needed something to manage them at scale.
TL;DR
Concept | What it is |
|---|---|
Dockerfile | Recipe for building your app |
Image | Frozen snapshot built from the Dockerfile |
Container | A running instance of an image |
Docker Compose | Tool to run multiple containers together |
Why it matters | Same environment everywhere = no more "works on my machine" |
Docker won't make your code better. But it will make sure the code you write actually runs the same way everywhere it goes.
If you’re a nerd and wanna learn more
The Only Docker tutorial You Need To Get Started - My tutorial
Thanks to everyone who submitted!
Manzolillom, kwame-Owusu, hamooo21112655, neilyneilynig, Nomekuma, iamsunildev, adnmzlz, sujitha483, Yaya9256, Ishaan282, and gcavelier!
Daily Temperatures
You are given an array of integers temperatures where temperatures[i] represents the daily temperatures on the ith day.
Return an array where output[i] is the number of days after the ith day before a warmer temperature appears on a future day. If there is no day in the future where a warmer temperature will appear for the ith day, set output[i] to 0 instead.
Examples
daily_temperatures([30,38,30,36,35,40,28])
output = [1,4,1,2,1,0,0]
daily_temperatures([22,21,20])
output = [0,0,0]
daily_temperatures([30,38,30,36,35,40,28])
output = [1,4,1,2,1,0,0]How To Submit Answers
Reply with
A link to your solution (github, twitter, personal blog, portfolio, replit, etc)
or if you’re on the web version leave a comment!
If you want to be mentioned here, I’d prefer if you sent a GitHub link or Replit!
That’s all from me!
Have a great week, be safe, make good choices, and have fun coding.
If I made a mistake or you have any questions, feel free to comment below or reply to the email!
See you all next week.
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