Claude for Coding and Technical Tasks

Claude is one of the most capable AI assistants for software development. Whether you're a beginner writing your first function or a senior developer reviewing architecture, Claude can help you write, understand, debug, and improve code.

Writing Code with Claude

Starting from Scratch

When you need Claude to write code, be specific about:

• The programming language
• What the code should do
• Any constraints or requirements
• How you'll use it

Good prompt:

Write a Python function called `parse_csv_emails` that:
- Reads a CSV file with columns: name, email, company
- Filters out rows where email is missing or invalid
- Returns a list of dictionaries with the valid rows
- Uses the csv module (no pandas)
- Include type hints

Claude will produce:

import csv
import re
from typing import TypedDict


class ContactRow(TypedDict):
    name: str
    email: str
    company: str


def parse_csv_emails(file_path: str) -> list[ContactRow]:
    """Read a CSV file and return rows with valid emails."""
    email_pattern = re.compile(r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$')
    valid_rows: list[ContactRow] = []

    with open(file_path, newline='', encoding='utf-8') as f:
        reader = csv.DictReader(f)
        for row in reader:
            email = row.get('email', '').strip()
            if email and email_pattern.match(email):
                valid_rows.append({
                    'name': row.get('name', '').strip(),
                    'email': email,
                    'company': row.get('company', '').strip(),
                })

    return valid_rows

Notice how Claude includes type hints, error handling, and clean structure without being asked for each one individually.

Building on Existing Code

When you have existing code, paste it and ask Claude to extend it:

Here's my existing Express.js route for getting users:

[paste your code]

Add a new route that handles POST /api/users to create
a new user. Validate that name and email are provided.
Follow the same patterns as the existing code.

Claude will match the style and patterns of your existing code rather than imposing its own.

Debugging with Claude

Describing the Problem

The more context you give about the bug, the faster Claude can help:

Bug: My React component re-renders infinitely when I add
this useEffect hook. The browser tab freezes.

Expected: The effect should run once when the component mounts
and fetch user data.

Here's the component:

[paste your code]

Reading Error Messages

Paste error messages directly — Claude is excellent at interpreting them:

I'm getting this error when I run my Node.js app:

TypeError: Cannot read properties of undefined (reading 'map')
    at UserList (/app/components/UserList.tsx:15:24)
    at renderWithHooks (node_modules/react-dom/...)

Here's UserList.tsx:

[paste the code]

Claude will trace the error to the specific line, explain why it's happening (likely users is undefined before the data loads), and suggest a fix (add a loading check or default value).

Systematic Debugging

For complex bugs, ask Claude to help you debug systematically:

This function works for most inputs but fails for certain edge cases.
I can't figure out which inputs cause the failure.

Help me identify potential edge cases that could break this function,
and suggest console.log statements to help me narrow down the issue.

[paste the code]

Code Review

Claude provides thorough, constructive code reviews. Here's how to get the most from them:

Full Review

Review this code for:
1. Bugs or logic errors
2. Security vulnerabilities
3. Performance issues
4. Readability improvements

Be specific — show me the problematic line and the fix.

[paste your code]

Focused Review

Review this database query function specifically for
SQL injection vulnerabilities and connection handling.
Assume this runs in a production Node.js application.

[paste your code]

Architecture Review

I've uploaded the key files from my project. Review the
overall architecture:
- Is the separation of concerns appropriate?
- Are there any patterns that will cause problems as we scale?
- What would you refactor first?

Explaining Code

Claude excels at making unfamiliar code understandable:

Line-by-Line Explanation

Explain this JavaScript code line by line.
I'm a beginner and don't understand closures yet.

const createCounter = () => {
  let count = 0;
  return {
    increment: () => ++count,
    decrement: () => --count,
    getCount: () => count,
  };
};

Understanding Patterns

What design pattern does this code use?
Explain why someone would choose this approach
and what alternatives exist.

[paste the code]

Reading Others' Code

I'm contributing to an open source project and need to
understand this file. Explain:
1. What this module does overall
2. The key functions and how they relate
3. Where I should look to add a new feature

[paste the code]

Learning to Code with Claude

Claude is a patient, knowledgeable tutor for learning programming:

Getting Explanations

Explain the difference between let, const, and var in JavaScript.
Use simple examples and tell me which one I should use
as a beginner.

Guided Practice

I'm learning Python and want to practice loops.
Give me a practice problem that's appropriate for a beginner
who understands variables and if statements but is new to loops.
After I attempt it, review my solution.

Understanding Concepts

I keep hearing about "REST APIs" but I don't really understand
what they are. Explain it like I'm someone who can use
the internet but has never programmed before.

Technical Writing with Claude

Claude can help with technical documentation:

README Files

Write a README.md for my project. Here's the context:
- It's a CLI tool that converts markdown files to PDF
- Written in Node.js
- Requires Node 18+
- Has 3 main commands: convert, batch, watch

Include: installation, quick start, command reference,
and contributing guidelines.

API Documentation

Here are my API route handlers. Generate API documentation
in a clear format with:
- Endpoint URL and method
- Request parameters
- Request body schema
- Response format
- Example request and response
- Error codes

[paste the route handlers]

Code Comments

Add clear, concise comments to this code. Don't comment
obvious things — focus on explaining the "why" behind
non-obvious decisions.

[paste the code]

Practical Workflows

Starting a New Project

I'm starting a new project: a task management CLI tool in Python.
Help me plan the initial structure:
1. Suggest a file/folder structure
2. List the key modules I'll need
3. Recommend libraries for CLI parsing and data storage
4. Write the initial main.py with argument parsing

Refactoring

This function works but it's 150 lines long and hard to maintain.
Help me refactor it into smaller, well-named functions.
Keep the same behavior — don't add features.

[paste the code]

Writing Tests

Write unit tests for this function using pytest.
Cover the main cases and edge cases you can identify.

[paste the function]

Tips for Coding with Claude

Tip 1: Paste Complete Code

Don't paraphrase your code — paste the actual code. Claude's analysis is only as good as what you show it.

Tip 2: Include Error Output

When debugging, include the full error message and stack trace, not just "it doesn't work."

Tip 3: Specify Your Environment

I'm using Python 3.11, Django 5.0, PostgreSQL 16,
running on Ubuntu 22.04.

Version information helps Claude give accurate, compatible suggestions.

Tip 4: Ask Why, Not Just How

Why does this approach use a hash map instead of a sorted array?
What tradeoffs are involved?

Understanding the reasoning helps you learn, not just copy solutions.

Tip 5: Verify Important Code

Claude writes good code, but it can still have bugs. Always test code before deploying to production, especially for:

• Security-sensitive operations
• Financial calculations
• Data migrations
• Authentication logic

Key Takeaways

• Be specific about language, requirements, and constraints when asking Claude to write code
• For debugging, always include the error message, expected behavior, and the actual code
• Claude provides thorough code reviews — ask for bug checks, security review, and architecture feedback
• Use Claude as a learning tool by asking for explanations, practice problems, and concept breakdowns
• Claude can help with technical writing: README files, API docs, and meaningful comments
• Always test Claude-generated code before using it in production