Regex clicks once you stop memorizing patterns and start thinking in pieces.

Core syntax

Useful patterns

# Email (basic)
[\w.+-]+@[\w-]+\.[a-zA-Z]{2,}

# URL
https?://[\w./-]+

# IPv4
\b\d{1,3}(\.\d{1,3}){3}\b

# Date YYYY-MM-DD
\d{4}-\d{2}-\d{2}

# Hex color
#[0-9a-fA-F]{6}

Python example

import re

text = "Contact: hello@example.com or support@test.org"
emails = re.findall(r'[\w.+-]+@[\w-]+\.[a-zA-Z]{2,}', text)
print(emails)  # ['hello@example.com', 'support@test.org']

Tip

Use regex101.com to test interactively. Always test on real data before deploying.

This is the question that confuses every developer at some point. Let’s settle it.

Merge

git checkout main
git merge feature-branch

Creates a merge commit. History shows exactly what happened: two branches joined at a point. Safe for shared branches.

Rebase

git checkout feature-branch
git rebase main

Rewrites your commits on top of main. History looks linear — as if you started the feature after main was updated.

If you’ve ever broken a project by upgrading a package globally, you need venvs.

What is a venv?

A virtual environment is an isolated Python installation — it has its own pip and packages, completely separate from your system Python.

Creating one

python -m venv .venv
source .venv/bin/activate    # Linux/macOS
.venv\Scripts\activate       # Windows

Installing packages

pip install requests numpy pandas
pip freeze > requirements.txt

Restoring later

python -m venv .venv
pip install -r requirements.txt

Using with conda

If you use conda, each conda create -n myenv python=3.11 works the same way — isolated by default.