Stop 14 · Build Your Data Science PortfolioProjects · 2/7

Kaggle Competition Submission

Part of the Data Science Roadmap

In short

Kaggle gives you real data, a fixed metric and a public scoreboard. It's the quickest way to see how your modelling compares with others and to learn tricks from people better than you.

Competing on a real Kaggle dataset gives you a public, comparable benchmark for your modeling skills and exposes you to techniques from top-scoring public notebooks.

The mascot breaks the finish ribbon on a running track with a small trophy waiting nearby.

Think of it like this

School sports day

Sports day is where you find out how fast you really are, running next to everyone else, timed by the same stopwatch. Kaggle does that for modelling: same data, same metric, one leaderboard. Studying how the winners ran afterwards is half the learning.

Watch it happen

From joining to submitting

Rules
EDA
Validation
Baseline
Improve
Submit

1/6Read the overview: the metric, the submission format, and any rules on external data.

The big ideas

What you need to know

Trust your CV

The public leaderboard scores only part of the test set. Chasing it often means overfitting to noise.

Submit a baseline early

A first submission catches format errors before you've spent days on features.

Learn from others

Read top public notebooks and discussions after trying yourself. Credit any idea you reuse.

Write it up

A short write-up of what worked and what didn't is what makes it a portfolio piece.

See it in code

Walk through the code

python
1import pandas as pd2from sklearn.ensemble import RandomForestClassifier3 4train = pd.read_csv("train.csv")5test = pd.read_csv("test.csv")6features = ["Pclass", "SibSp", "Parch"]7 8model = RandomForestClassifier(n_estimators=200, random_state=1)9model.fit(train[features], train["Survived"])10 11sub = pd.DataFrame({"PassengerId": test["PassengerId"],12                    "Survived": model.predict(test[features])})13sub.to_csv("submission.csv", index=False)

1/3Load the competition files and choose a few simple numeric columns with no missing values.

A bare-bones submission for Kaggle's Titanic starter competition. Get this working first, then improve the features.

Save yourself the pain

Common mistakes

Oops

Picking your final model because it ranked highest on the public leaderboard.

Do this instead

Choose by local cross-validation. The private leaderboard, which decides final ranks, often reshuffles public toppers.

Oops

Forking a top notebook, submitting it and calling it your project.

Do this instead

Build your own pipeline first, then borrow ideas with credit and explain why they helped.

Your mission

Your first submission

~45 min

Quick check

Your 5-fold CV score went up, but your public leaderboard score dropped slightly. What should you trust more?

Go deeper

  1. 1Pick a beginner-friendly Kaggle competition and submit at least one full solution.
  2. 2Read 2-3 top public notebooks after submitting to see what techniques you missed.
  3. 3Document your leaderboard score and what you learned, even if it's not a top rank.

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