Day 12 | How to Dockerize a Flask Python Application | Dockerfile + Build + Run
🐳 Welcome to Day 12 of the Docker Zero to Hero series!
In this video I'll show you how to containerize a Flask
Python application from scratch — write the Dockerfile,
install dependencies using requirements.txt, build the image,
run with port mapping and test it live!
I'll also show you the manual way first so you can clearly
see why Docker makes Flask deployment so much cleaner
and more reliable!
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🎯 WHY EVERY PYTHON DEVELOPER NEEDS TO KNOW THIS
Flask is one of the most popular Python web frameworks
used in startups, microservices and APIs across the industry.
But deploying Flask manually means managing Python versions,
virtual environments, dependency conflicts and
environment differences across machines.
Docker eliminates all of this by packaging your Flask app
and all its dependencies into a single portable container
that runs identically on any machine.
This is a core skill for every Python developer
moving into DevOps or cloud deployment roles.
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📌 WHAT YOU WILL LEARN IN THIS VIDEO
✅ How to run Flask application manually — the old way
✅ Problems with manual Flask deployment
✅ How to write a Dockerfile for Flask Python application
✅ What is requirements.txt and why it is needed in Docker
✅ How to install Python dependencies inside Docker image
✅ How to build Docker image for Flask application
✅ How to run Flask container with correct port mapping
✅ How to test Flask application using curl or browser
✅ Manual vs Docker deployment comparison
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🔍 WHO IS THIS VIDEO FOR
This video is perfect for you if you are:
👉 A Python developer who wants to containerize Flask apps
👉 A DevOps engineer working with Python microservices
👉 Someone preparing for Docker or Python deployment interviews
👉 A backend developer moving their Flask app to cloud
👉 Anyone who has struggled with Python dependency
conflicts across different environments
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💡 MANUAL VS DOCKER DEPLOYMENT
❌ Manual Flask Deployment Problems
→ Need to install Python on every machine separately
→ Virtual environment setup required on each machine
→ Dependency versions differ across environments
→ Works on dev machine but breaks on server
→ Hard to replicate across team members machines
✅ Docker Flask Deployment Benefits
→ Python and all dependencies packaged inside container
→ No virtual environment management needed
→ Runs identically on every machine
→ Single Dockerfile replaces all setup instructions
→ Share image — anyone can run it instantly
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💡 FLASK DOCKERFILE EXPLAINED
FROM python:3.9-slim
→ Use official Python slim image as base
→ Slim version is smaller than full Python image
WORKDIR /app
→ Set working directory inside container
COPY requirements.txt .
→ Copy requirements file first for better layer caching
RUN pip install -r requirements.txt
→ Install all Python dependencies
COPY . .
→ Copy rest of application code
EXPOSE 5000
→ Document that Flask runs on port 5000
CMD ["python", "app.py"]
→ Command to start Flask application
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⚙️ WHAT IS COVERED IN THE LIVE DEMO
→ Running Flask application manually first
→ Showing dependency setup required manually
→ Writing Dockerfile for Flask step by step
→ Creating requirements.txt with Flask dependency
→ Building Docker image using docker build
→ Running container with -p 5000:5000 port mapping
→ Testing application using curl request
→ Comparing both approaches side by side
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⚠️ COMMON MISTAKES BEGINNERS MAKE
→ Not copying requirements.txt before application code
Copy requirements.txt first for Docker layer caching benefits
→ Using full Python image instead of slim
python:3.9-slim is much smaller — always prefer slim
→ Wrong port mapping — Flask runs on 5000 not 8080
Use -p 5000:5000 for Flask applications
→ Not setting WORKDIR in Dockerfile
Always set WORKDIR to keep container filesystem organized
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🔔 SUBSCRIBE TO ayushbuildstech
If you are serious about learning Docker and DevOps
with real hands on tutorials —
Subscribe to ayushbuildstech and hit the bell icon
so you never miss a video in this series!
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👍 FOUND THIS HELPFUL?
If this video helped you Dockerize your Flask app —
smash the Like button and subscribe for Day 13!
💬 COMMENT BELOW:
Are you currently running Flask applications manually
or inside Docker?
Comment below — would love to know!
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