opensheet-core 0.1.0

A fast, memory-efficient spreadsheet I/O library for Python

Features  •  Benchmarks  •  Installation  •  Quick Start  •  API  •  Roadmap  •  Contributing

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Why OpenSheet Core?

Existing Python spreadsheet libraries force you to choose between performance, memory efficiency, broad format support, and easy installation. OpenSheet Core eliminates that tradeoff with a native Rust core exposed through a clean Python API — installable with a single pip install.

Features

• Streaming XLSX reader — row-by-row iteration without loading the entire file into memory
• Streaming XLSX writer — write millions of rows with constant memory usage
• Formula support — read and write formulas with optional cached values
• Typed cell extraction — strings, numbers, booleans, formulas, and empty cells are returned as native Python types
• Context manager support — Pythonic with statement for safe resource management
• Cross-platform — tested on Linux, macOS, and Windows across Python 3.9–3.13
• Zero Python dependencies — single native extension, no dependency tree to manage

Benchmarks

Benchmarked against openpyxl on a 100,000-row dataset:

Operation	OpenSheet Core	openpyxl	Speedup	Memory
Write	~0.7s	~1.8s	2.5x faster	~300x less
Read	~0.9s	~2.4s	2.7x faster	Low & constant

Memory usage stays flat regardless of file size thanks to streaming architecture.

Installation

pip install opensheet-core

From source (requires Rust toolchain)

pip install maturin
git clone https://github.com/0xNadr/opensheet-core
cd opensheet-core
maturin develop --release

Quick Start

Reading an XLSX file

from opensheet_core import read_xlsx, read_sheet

# Read all sheets
sheets = read_xlsx("report.xlsx")
for sheet in sheets:
    print(f"Sheet: {sheet['name']}")
    for row in sheet["rows"]:
        print(row)  # List of typed Python values

# Read a specific sheet
rows = read_sheet("report.xlsx", sheet_name="Data")

Writing an XLSX file

from opensheet_core import XlsxWriter

with XlsxWriter("output.xlsx") as writer:
    writer.add_sheet("Data")
    writer.write_row(["Name", "Age", "Active"])
    writer.write_row(["Alice", 30, True])
    writer.write_row(["Bob", 25, False])

Writing formulas

from opensheet_core import XlsxWriter, Formula

with XlsxWriter("output.xlsx") as writer:
    writer.add_sheet("Budget")
    writer.write_row(["Item", "Cost"])
    writer.write_row(["Rent", 1200])
    writer.write_row(["Food", 400])
    writer.write_row(["Total", Formula("SUM(B2:B3)", cached_value=1600)])

API Reference

read_xlsx(path: str) -> list[dict]

Reads an XLSX file and returns a list of dicts with "name" (str) and "rows" (list of lists). Each cell is a typed Python value (str, int, float, bool, Formula, or None).

read_sheet(path, sheet_name=None, sheet_index=None) -> list[list]

Reads a single sheet by name or index. Returns the first sheet by default.

sheet_names(path: str) -> list[str]

Returns the list of sheet names in a workbook.

XlsxWriter(path: str)

Streaming XLSX writer. Use as a context manager.

Method	Description
add_sheet(name: str)	Create a new worksheet
write_row(values: list)	Write a row of values to the current sheet
close()	Finalize and close the file

Formula(formula: str, cached_value=None)

Represents a spreadsheet formula. Pass as a cell value when writing, and received when reading cells that contain formulas.

Architecture

┌──────────────────────────┐
│      Python API          │  ← opensheet_core (PyO3 bindings)
├──────────────────────────┤
│      Rust Core           │  ← Streaming parser & writer
│  ┌────────┐ ┌──────────┐ │
│  │ Reader │ │  Writer  │ │
│  │ (SAX)  │ │ (Stream) │ │
│  └────────┘ └──────────┘ │
├──────────────────────────┤
│  quick-xml  │    zip     │  ← Dependencies
└──────────────────────────┘

Roadmap

• XLSX reading with typed cell extraction
• Streaming XLSX writing with low memory usage
• Formula read/write support
• Python bindings via PyO3
• CI across Linux, macOS, Windows (Python 3.9–3.13)
• Benchmarks vs openpyxl
• Prebuilt wheels on PyPI
• Merged cell metadata
• Basic cell styling
• Date/time cell support
• Broader test corpus & fuzzing

Project Status

v0.2.0 — functional reader and writer with formula support, 24 passing tests, and prebuilt wheels on PyPI. The API may change before 1.0.

Contributing

Contributions are welcome! Here are some great ways to get involved:

• Report bugs or real-world spreadsheet edge cases
• Submit representative sample files for testing
• Suggest benchmark scenarios
• Improve documentation
• Open PRs for roadmap items

License

MIT

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_{Built with Rust and PyO3  |  Open digital infrastructure for the Python ecosystem}