fastpyxl 1.0.9

A high-performance Python library to read/write Excel 2010 xlsx/xlsm files

A high-performance, statically typed drop-in replacement for openpyxl.

fastpyxl reads and writes Excel 2010+ xlsx/xlsm/xltx/xltm files with the same API as openpyxl — just change your import:

# before
from openpyxl import Workbook, load_workbook

# after
from fastpyxl import Workbook, load_workbook

No other code changes required.

Performance

Benchmarked on a real-world 5.2 MB IMF/World Bank workbook (887,370 cells, 97k formulas). Median of 5 runs, Python 3.12, openpyxl 3.1.5:

Operation	openpyxl	fastpyxl	Change
Load workbook	7.29s	5.58s	-23.5%
Save workbook	5.70s	5.74s	+0.6%
Read-only iteration	4.84s	4.07s	-15.9%

Key optimizations since 1.0.0: inlined cell parsing, O(1) sheet lookup, formula translation fast path, VBA archive filtering, empty-cell skip, and cached sheet names. See the changelog for details.

Installation

pip install fastpyxl

Quick start

from fastpyxl import Workbook

wb = Workbook()
ws = wb.active

ws["A1"] = 42
ws.append([1, 2, 3])

import datetime
ws["A2"] = datetime.datetime.now()

wb.save("sample.xlsx")

Key features

• 1-to-1 API compatibility with openpyxl

• Static typing throughout

• Optimized cell parsing, coordinate lookups, and style deduplication

• Read-only and write-only modes for large files

• Charts, images, comments, data validation, pivot tables

• Conditional formatting and rich text

• Pandas DataFrame integration

Security

By default fastpyxl does not guard against quadratic blowup or billion laughs XML attacks. To guard against these attacks install defusedxml.

Documentation

Full documentation: https://fastpyxl.readthedocs.io

• Tutorial

• API reference

• Release notes

Acknowledgements

fastpyxl is a fork of openpyxl. All credit to Eric Gazoni, Charlie Clark, and the openpyxl contributors whose work this project builds upon.

License

MIT. See LICENSE for details.