Python Formatter

Quick Start Guide

1. Paste Code: Copy your unformatted or messy Python code into the input area
2. Configure Options: Choose indent size (2 or 4 spaces), max line length, and quote style
3. Format: Click "Format Code" to beautify your Python code
4. Copy or Download: Use the output buttons to copy or download the formatted code
5. Try Examples: Click example buttons to see different Python formatting scenarios

What is Python Formatting?

Python formatting (also called code beautification or style normalization) transforms messy, inconsistent, or poorly formatted Python code into clean, PEP 8-compliant code with proper indentation, spacing, and line breaks.

Purpose: Code readability, PEP 8 compliance, team consistency Input: Unformatted, messy, or inconsistent Python code Output: Clean, PEP 8-compliant, readable Python code Usage: Development, code review, learning, maintaining standards

Why Format Python Code?

Development Benefits:

• Enforce PEP 8 style guidelines automatically
• Standardize code style across your team
• Make code reviews faster and more effective
• Improve code readability and maintainability
• Clean up code from online sources or tutorials
• Learn Python best practices through examples

Common Scenarios:

• Formatting code copied from Stack Overflow or tutorials
• Cleaning up legacy Python codebases
• Enforcing team coding standards
• Preparing code for code reviews
• Learning proper Python style
• Migrating from other languages to Python

PEP 8 Style Guidelines

PEP 8 is Python's official style guide. Key points:

Indentation:

• Use 4 spaces per indentation level (not tabs)
• Continuation lines should align wrapped elements

Line Length:

• Limit lines to 79 characters (PEP 8 strict)
• 88 characters (Black default)
• 120 characters (relaxed, some teams)

Blank Lines:

• 2 blank lines around top-level functions and classes
• 1 blank line around methods inside classes

Whitespace:

• No spaces inside brackets: spam(ham[1], {eggs: 2})
• Space around operators: x = 1 + 2
• Space after commas: def func(a, b, c):

Naming:

• Functions/variables: lowercase_with_underscores
• Classes: CapitalizedWords
• Constants: ALL_CAPS_WITH_UNDERSCORES

Formatting Options Explained

Indent Size

4 spaces (PEP 8 recommended):

• Official Python standard
• Most widely used in Python community
• Required for contributing to Python stdlib

2 spaces:

• More compact, saves vertical space
• Common in web development
• Not PEP 8 compliant

When to use:

• 4 spaces: Almost always (PEP 8 standard)
• 2 spaces: Only if team requires it

Max Line Length

79 characters (PEP 8):

• Traditional limit for code
• Allows side-by-side code review
• Works well with 80-character terminals

88 characters (Black):

• Default for Black formatter
• Good compromise between readability and compactness
• Modern Python standard

120 characters (Relaxed):

• More permissive
• Reduces line wrapping
• Common in modern editors

Recommendation: 88 for most projects, 79 for strict PEP 8

Quote Style

Keep as-is:

• Preserve original quote style
• Mix of single and double quotes

Single quotes:

• PEP 8 allows both, no preference
• Slightly cleaner for strings with apostrophes
• name = 'John'

Double quotes:

• PEP 8 allows both, no preference
• Better for strings with single quotes inside
• name = "John"

Recommendation: Be consistent within project

Common Use Cases

1. Formatting Functions and Classes

Purpose: Clean up function and class definitions

Before:

def calculate_total(
items,tax_rate=0.1):
total=sum(
item['price']
for item in items);
return total*(
1+tax_rate)

class ShoppingCart:
def __init__(self):
self.items=[];
def add_item(self,
item):
self.items.append(
item);

After (formatted with 4-space indent):

def calculate_total(
    items,
    tax_rate=0.1
):
    total = sum(
        item['price']
        for item in items
    )
    return total * (
        1 + tax_rate
    )


class ShoppingCart:
    def __init__(self):
        self.items = []

    def add_item(self, item):
        self.items.append(item)

2. Formatting List Comprehensions

Purpose: Make complex comprehensions readable

Before:

numbers=[1,2,3,4,5,6,7,8,9,10];
squares=[x**2 for x in numbers
if x%2==0];
matrix=[[1,2,3],[4,5,6],
[7,8,9]];
flattened=[item for row
in matrix for item in row];
result={x:x**2 for x
in range(10)if x%2==0}

After:

numbers = [
    1, 2, 3, 4, 5,
    6, 7, 8, 9, 10
]

squares = [
    x**2 for x in numbers
    if x % 2 == 0
]

matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

flattened = [
    item
    for row in matrix
    for item in row
]

result = {
    x: x**2
    for x in range(10)
    if x % 2 == 0
}

3. Formatting Decorators

Purpose: Clean up decorator syntax

Before:

from functools import wraps
def timing_decorator(func):
@wraps(func);def wrapper(
*args,**kwargs):
import time;start=time.time();
result=func(*args,**kwargs);
end=time.time();
print(f"Took {end-start:.2f}s");
return result;return wrapper

@timing_decorator;
def slow_function():
import time;time.sleep(1);
return "Done"

After:

from functools import wraps


def timing_decorator(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        import time
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"Took {end-start:.2f}s")
        return result
    return wrapper


@timing_decorator
def slow_function():
    import time
    time.sleep(1)
    return "Done"

4. Formatting Error Handling

Purpose: Make try-except blocks readable

Before:

def divide_numbers(a,b):
try:result=a/b;return result;
except ZeroDivisionError as e:
print(f"Error: {e}");
return None;except TypeError:
print("Invalid types");
return None;finally:
print("Operation complete")

After:

def divide_numbers(a, b):
    try:
        result = a / b
        return result
    except ZeroDivisionError as e:
        print(f"Error: {e}")
        return None
    except TypeError:
        print("Invalid types")
        return None
    finally:
        print("Operation complete")

5. Formatting Type Hints and Dataclasses

Purpose: Clean up modern Python type annotations

Before:

from dataclasses import dataclass;
from typing import List,Optional,Dict

@dataclass;class User:name:str;
email:str;age:int;
tags:List[str];
metadata:Optional[Dict[str,any]]=None;
def greet(self)->str:
return f"Hello, {self.name}!"

After:

from dataclasses import dataclass
from typing import List, Optional, Dict


@dataclass
class User:
    name: str
    email: str
    age: int
    tags: List[str]
    metadata: Optional[Dict[str, any]] = None

    def greet(self) -> str:
        return f"Hello, {self.name}!"

6. Formatting Async/Await Code

Purpose: Clean up asynchronous Python code

Before:

import asyncio
async def fetch_data(url:str)->dict:
async with aiohttp.ClientSession()
as session:async with session.get(
url)as response:return await
response.json()

async def main():tasks=[
fetch_data(
f"https://api.example.com/{i}")
for i in range(5)];
results=await asyncio.gather(
*tasks);return results

After:

import asyncio


async def fetch_data(
    url: str
) -> dict:
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            return await response.json()


async def main():
    tasks = [
        fetch_data(
            f"https://api.example.com/{i}"
        )
        for i in range(5)
    ]
    results = await asyncio.gather(*tasks)
    return results

Features

Core Functionality

• PEP 8 Compliance: Format code following Python style guidelines
• Automatic Indentation: Proper 4-space indentation
• Whitespace Normalization: Correct spacing around operators
• Line Break Management: Insert breaks for readability
• Comment Preservation: Keep all comments intact
• String Safety: Never modify string contents
• Docstring Handling: Preserve triple-quoted strings

Supported Python Features

Basic Syntax:

• Function definitions (def)
• Class definitions (class)
• Conditional statements (if, elif, else)
• Loops (for, while)
• Exception handling (try, except, finally)

Advanced Features:

• Decorators (@decorator)
• Context managers (with)
• List/dict/set comprehensions
• Generator expressions
• Lambda functions
• Type hints and annotations

Modern Python:

• Async/await syntax
• F-strings
• Dataclasses
• Match/case statements (Python 3.10+)
• Walrus operator (:=)

Formatting Controls

Indent Size:

• 2 spaces (compact)
• 4 spaces (PEP 8 standard)

Max Line Length:

• 79 characters (PEP 8 strict)
• 88 characters (Black default)
• 120 characters (relaxed)

Quote Style:

• Keep as-is (preserve original)
• Single quotes (normalize to ')
• Double quotes (normalize to "")

Best Practices

1. Follow PEP 8

Recommended settings:

• Indent: 4 spaces
• Max line: 88 characters
• Quotes: Consistent (single or double, pick one)

2. Use Black Style for Modern Projects

Black settings:

• Indent: 4 spaces
• Max line: 88 characters
• Quotes: Double
• No configuration needed

3. Format Before Committing

Workflow:

1. Write your Python code
2. Format before committing
3. Run linter (pylint, flake8)
4. Run type checker (mypy)
5. Commit formatted code

4. Combine with Linters

Recommended tools:

• Black: Automatic formatting
• flake8: Style checking
• pylint: Code quality
• mypy: Type checking
• isort: Import sorting

5. Set Up Pre-commit Hooks

# .pre-commit-config.yaml
repos:
  - repo: https://github.com/psf/black
    rev: 23.1.0
    hooks:
      - id: black
  - repo: https://github.com/pycqa/flake8
    rev: 6.0.0
    hooks:
      - id: flake8

Technical Details

How Python Formatting Works

1. Parse input code character by character
2. Track context (strings, comments, indentation)
3. Identify blocks (functions, classes, if/for/while)
4. Apply proper indentation (4 spaces per level)
5. Add spacing around operators
6. Insert blank lines between functions/classes
7. Apply quote style preferences
8. Output PEP 8-compliant code

Limitations

This is a basic formatter:

• Uses character-based parsing (not full AST)
• May not handle all edge cases
• Works well for most common Python patterns
• Not a replacement for Black or autopep8

For production projects, consider:

• Black: Opinionated, zero-config formatter
• autopep8: Automatic PEP 8 formatting
• yapf: Configurable formatter from Google
• blue: Black fork with different defaults

This tool is best for:

• Quick one-off formatting
• Learning Python style
• Formatting code snippets
• Simple formatting tasks
• Privacy-focused use (100% local)

Supported Syntax

✅ Fully supported:

• Function and class definitions
• If/elif/else statements
• For and while loops
• Try/except/finally blocks
• List/dict comprehensions
• Decorators
• Import statements
• Comments and docstrings

⚠️ Limited support:

• Very complex nested comprehensions
• Multi-line string formatting
• Advanced f-string expressions
• Some edge cases with operators

Performance

Processing speed:

• Small files (<10KB): Instant
• Medium files (10-100KB): <1 second
• Large files (100KB-500KB): 1-2 seconds
• Very large files (>500KB): May be slow

Browser-based:

• All processing in your browser
• No server uploads or delays
• Works offline after initial load
• RAM usage: ~2-5MB per 100KB

Troubleshooting

Issue: Output looks wrong

Possible causes:

1. Input has syntax errors
2. Complex edge case not handled
3. String content being modified

Solutions:

• Check Python syntax first
• Try different formatting options
• Use Black for complex code
• Report issues with examples

Issue: Indentation is incorrect

Possible causes:

1. Mixed tabs and spaces in original
2. Inconsistent indentation
3. Complex nesting

Solutions:

• Convert tabs to spaces first
• Check original indentation
• Use 4 spaces (PEP 8 standard)
• Try Black for perfect indentation

Issue: Code doesn't run after formatting

This shouldn't happen - formatting preserves logic

If it does:

1. Original code likely had errors
2. Compare with original carefully
3. Check for syntax errors
4. Report issue with example

Browser Compatibility

Supported browsers:

• ✅ Chrome 90+ (recommended)
• ✅ Firefox 88+
• ✅ Safari 14+
• ✅ Edge 90+
• ✅ Opera 76+

Required features:

• ES6+ JavaScript support
• Clipboard API (for copy)
• Blob API (for download)
• Modern CSS (for UI)

Works on:

• Desktop: Windows, macOS, Linux
• Mobile: iOS Safari, Chrome Android
• Tablets: iPad, Android tablets

Privacy & Security

Client-Side Processing

• 100% Local: All formatting in your browser
• No Uploads: Code never sent to any server
• No Storage: Nothing saved or cached
• No Tracking: No analytics on your code
• No Accounts: No login required

Security Features

• Sandboxed: Runs in browser security sandbox
• No Execution: Code never executed, only parsed
• Safe Parsing: Character-based, not eval-based
• No External Calls: No network requests

Safe for Sensitive Code

• ✅ Proprietary Python code
• ✅ Client projects
• ✅ Production code
• ✅ Code with business logic
• ✅ Personal projects

Important: Remove API keys, passwords, and secrets before formatting.

Comparison with Other Tools

Python Formatter vs Black

Python Formatter (this tool):

• ✅ Browser-based, instant access
• ✅ Configurable options
• ✅ No installation required
• ✅ Privacy-focused (100% local)
• ❌ Basic parsing, not AST-based
• ❌ Limited edge case handling

Black:

• ✅ Full AST parsing, perfect output
• ✅ Industry standard for Python
• ✅ Zero configuration needed
• ✅ Handles all edge cases
• ❌ Requires pip installation
• ❌ Opinionated (no options)

When to use this tool: Quick formatting, learning, one-off tasks

When to use Black: Production projects, team collaboration

Python Formatter vs autopep8

This tool: Quick browser-based formatting autopep8: Command-line PEP 8 formatter

autopep8 advantages:

• Full PEP 8 compliance
• Fixes many issues automatically
• Command-line integration

This tool advantages:

• No installation needed
• Works in browser
• Instant access
• Privacy-focused

Integration Tips

Using Formatted Code

1. Copy to Editor:

• Format your Python code
• Click "Copy Output"
• Paste into your editor
• Test the code

2. Download File:

• Format code
• Click "Download .py"
• Replace original file
• Run and test

3. Combine with Git:

# Format Python code
# Then in terminal:
python -m py_compile file.py  # Check syntax
pytest  # Run tests
git add .
git commit -m "Format Python code"

Setting Up Team Standards

1. Document style:

• Indent: 4 spaces (PEP 8)
• Max line: 88 (Black standard)
• Quotes: Single or double (be consistent)

2. Add to project:

• Include in README or CONTRIBUTING.md
• Add .editorconfig file
• Create pyproject.toml for Black
• Set up pre-commit hooks

3. Code review checklist:

• PEP 8 compliant indentation
• Proper spacing around operators
• Blank lines between functions
• Consistent quote style

Quick Reference

Recommended Settings

PEP 8 Strict:

• Indent: 4 spaces
• Max line: 79
• Quotes: Consistent

Black Style (Modern):

• Indent: 4 spaces
• Max line: 88
• Quotes: Double

Learning Python:

• Indent: 4 spaces (standard)
• Max line: 88 (readable)
• Quotes: Keep as-is (see examples)

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Note: For production Python projects, we strongly recommend using Black for automatic formatting or autopep8 for PEP 8 compliance. This tool is perfect for quick formatting, learning Python style, and privacy-focused use cases.