H9A — How Many 9 in 1 to 100

A CLI tool and Python library that counts how many times a digit appears in a range of numbers, with a colorized step-by-step breakdown.

Overview

H9A is an installable Python package that counts how many times a given digit appears in a range of numbers (by default: the digit 9 between 1 and 100). It provides both a h9a command-line tool and an importable library, and it prints each step of the calculation — the per-place counts and the combined total — as styled, colorized output. It is built with rich for console formatting, pyfiglet for an ASCII-art banner, and Pillow for optional terminal-style screenshots.

Screenshot

More screenshots: View all screenshots

The screenshot above is generated by the tool itself. Regenerate it at any time with h9a --screenshot.

Table of Contents

• Overview
• Screenshot
• Key Features
• Installation
• Quick Start
• Usage Examples
• Documentation
• Interface
• Architecture
• Requirements
• Prerequisites
• Development
• Contributing
• Security
• License
• Acknowledgments

Key Features

• Installable package — pip install h9a provides the h9a command and the h9a importable library (h9a/core.py).
• CLI with options — --digit, --start, --end, --json, --no-color, --screenshot, and --version (h9a/cli.py).
• Library API — count_digit() returns a DigitCount with a per-place breakdown; build_lines(), render_text(), and generate_screenshot() are available to other programs (h9a/__init__.py).
• Instant results on huge ranges — count_digit() uses a closed-form, per-place formula, so ranges like 1 to 1,000,000,000 are counted instantly instead of being iterated number by number.
• Step-by-step calculation — prints the count for each decimal place (ones, tens, hundreds, ...) and the running total.
• Colorized output — uses the rich library for styled, readable console output.
• ASCII-art banner — renders "H9A" with pyfiglet (h9a/render.py).
• Screenshot generation — renders the output to a terminal-style PNG image with Pillow (h9a/screenshot.py, Screenshots/home.png).

Installation

From PyPI

python -m pip install h9a

For screenshot support, install the extra:

python -m pip install "h9a[screenshot]"

From the repository

git clone https://github.com/rkriad585/h9a.git
cd h9a
python -m pip install .

For development, install in editable mode with the screenshot extra:

python -m pip install -e .[screenshot]

Dependencies

• rich
• pyfiglet
• Pillow (optional — only needed for --screenshot / generate_screenshot)

Full instructions are in docs/installation.md.

Quick Start

python -m pip install rich pyfiglet
python -m h9a

If you installed the package, you can also use the console script directly:

h9a

Usage Examples

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How Many 9 In 1 to 100

Calculating step by step...
Step 2: 9 appears 10 times in the ones place.
Step 3: 9 appears 10 times in the tens place.
Step 4: Total occurrences of 9 = 20.

Explanation:
1. In the ones place: The digit 9 appears in numbers like 9, 19, 29, ..., 99.
2. In the tens place: The digit 9 appears in numbers like 90, 91, 92, ..., 99.
3. Total occurrences are calculated by adding these together.

Final Result: In the range 1 to 100, the digit '9' appears 20 times!

Count a different digit over a different range:

h9a --digit 5 --start 1 --end 50

Machine-readable output:

h9a --json

{
  "digit": 9,
  "start": 1,
  "end": 100,
  "by_position": {
    "1": 10,
    "10": 10
  },
  "total": 20
}

Documentation

Interface

Command line

The h9a command takes no positional arguments:

h9a [--digit DIGIT] [--start START] [--end END] [--json] [--no-color] [--screenshot [PATH]] [--version]

Exit codes: 0 on success, 2 on invalid arguments.

Library

from h9a import count_digit

result = count_digit(digit=9, start=1, end=100)
print(result.total)        # 20
print(result.by_position)  # {1: 10, 10: 10}

See docs/api.md for the full library reference.

Architecture

The project is an installable Python package. The h9a package contains four modules:

flowchart TD
    CLI["h9a/cli.py (argparse)"]
    API["h9a/__init__.py (public API)"]
    Core["h9a/core.py - count_digit()"]
    Render["h9a/render.py - build_lines()"]
    Shot["h9a/screenshot.py - generate_screenshot()"]
    CLI --> Core
    CLI --> Render
    CLI --> Shot
    API --> Core
    API --> Render
    API --> Shot
    Render --> Core
    Shot --> Render

h9a/
├── .github/
│   └── workflows/
│       ├── docs.yml            # documentation -> GitHub Pages
│       └── publish-container.yml  # container -> GHCR
├── Dockerfile
├── LICENSE                 # MIT
├── README.md
├── Screenshots/
│   └── home.png            # generated by `h9a --screenshot`
├── docs/                   # project documentation
├── h9a/                    # installable package
│   ├── __init__.py         # public API
│   ├── __main__.py         # python -m h9a
│   ├── cli.py              # h9a command-line interface
│   ├── core.py             # counting logic
│   ├── render.py           # styled output lines
│   └── screenshot.py       # Pillow screenshot generator
├── logo/
│   └── logo.svg
├── pyproject.toml          # package metadata and h9a entry point
└── tests/                  # pytest suite

Requirements

• Python 3.8 or later
• rich
• pyfiglet
• Pillow (optional — only for --screenshot / generate_screenshot)

Prerequisites

• A working Python 3.8+ installation with pip
• git to clone the repository
• A terminal that supports ANSI colors for the best visual output (colors are optional — the text is readable without them)

Development

git clone https://github.com/rkriad585/h9a.git
cd h9a
python -m pip install -e .[screenshot]
h9a

Run the checks with pytest, ruff, and mypy (installed via python -m pip install -e ".[dev]"). GitHub Actions deploys the documentation to GitHub Pages and publishes the container image to GitHub Container Registry. See docs/development.md.

Contributing

Contributions are welcome. Please read CONTRIBUTING.md and the Code of Conduct before opening a pull request.

Security

Please report security issues privately as described in SECURITY.md.

License

This project is licensed under the MIT License. See the LICENSE file for details.

Acknowledgments

• RK Riad Khan — author and maintainer.
• Built with the rich, pyfiglet, and Pillow libraries.