[Solved] You wrote this Dockerfile for your Flask app:FROM python:3.12-slim COPY app.py /app/ CMD ["python", "app.py"]When you run the container, the app crashes with "ModuleNotFoundError: flask".... | Flask

Flask - Deployment

You wrote this Dockerfile for your Flask app:

FROM python:3.12-slim
COPY app.py /app/
CMD ["python", "app.py"]

When you run the container, the app crashes with "ModuleNotFoundError: flask". What is the problem?

AFlask is not installed inside the container

Bapp.py is not copied to the container

CCMD syntax is incorrect

DPython version 3.12-slim does not support Flask

Step-by-Step Solution

Solution:

Step 1: Check Dockerfile for dependency installation
No RUN command installs Flask or dependencies inside container.
Step 2: Understand error cause
ModuleNotFoundError means Flask package missing in container environment.
Final Answer:
Flask is not installed inside the container -> Option A
Quick Check:
Missing Flask install causes ModuleNotFoundError = C [OK]

Quick Trick: Always RUN pip install for dependencies inside Dockerfile [OK]

Common Mistakes:

MISTAKES

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