pyopenxlsx 0.3.1

Python bindings for OpenXLSX using nanobind

PyOpenXLSX

pyopenxlsx is a high-performance Python binding for the OpenXLSX C++ library. It aims to provide significantly faster read/write speeds compared to pure Python libraries like openpyxl, while maintaining a Pythonic API design.

Core Features

• High Performance: Powered by the modern C++17 OpenXLSX library.
• Pythonic API: Intuitive interface with properties, iterators, and context managers.
• Async Support: async/await support for key I/O operations.
• Rich Styling: comprehensive support for fonts, fills, borders, alignments, and number formats.
• Memory Safety: Combines C++ efficiency with Python's automatic memory management.

Tech Stack

Component	Technology
C++ Core	OpenXLSX
Bindings	nanobind
Build System	scikit-build-core & CMake

Installation

From PyPI (Recommended)

# Using pip
pip install pyopenxlsx

# Using uv
uv pip install pyopenxlsx

From Source

# Using uv
uv pip install .

# Or using pip
pip install .

Development Installation

uv pip install -e .

Quick Start

Create and Save a Workbook

from pyopenxlsx import Workbook

# Create a new workbook
with Workbook() as wb:
    ws = wb.active
    ws.title = "MySheet"
    
    # Write data
    ws["A1"].value = "Hello"
    ws["B1"].value = 42
    ws.cell(row=2, column=1).value = 3.14
    
    # Save
    wb.save("example.xlsx")

Read a Workbook

from pyopenxlsx import load_workbook

wb = load_workbook("example.xlsx")
ws = wb["MySheet"]
print(ws["A1"].value)  # Output: Hello
wb.close()

Async Operations

pyopenxlsx provides async/await support for all I/O-intensive operations, ensuring your event loop remains responsive.

import asyncio
from pyopenxlsx import Workbook, load_workbook_async, Font

async def main():
    # 1. Async context manager for automatic cleanup
    async with Workbook() as wb:
        ws = wb.active
        ws["A1"].value = "Async Data"
        
        # 2. Async stylesheet creation
        style_idx = await wb.add_style_async(font=Font(bold=True))
        ws["A1"].style_index = style_idx
        
        # 3. Async worksheet operations
        new_ws = await wb.create_sheet_async("AsyncSheet")
        await new_ws.append_async(["Dynamic", "Row", 123])
        
        # 4. Async range operations
        await new_ws.range("A1:C1").clear_async()
        
        # 5. Async save
        await wb.save_async("async_example.xlsx")

    # 6. Async load
    async with await load_workbook_async("async_example.xlsx") as wb:
        ws = wb.active
        print(ws["A1"].value)
        
        # 7. Async protection
        await ws.protect_async(password="secret")
        await ws.unprotect_async()

asyncio.run(main())

Styling

from pyopenxlsx import Workbook, Font, Fill, Border, Side, Alignment

wb = Workbook()
ws = wb.active

# Define styles using hex colors (ARGB) or names
# Hex colors can be 6-digit (RRGGBB) or 8-digit (AARRGGBB)
font = Font(name="Arial", size=14, bold=True, color="FF0000") # Red
fill = Fill(pattern_type="solid", color="FFFF00")              # Yellow
border = Border(
    left=Side(style="thin", color="000000"),
    right=Side(style="thin"),
    top=Side(style="thick"),
    bottom=Side(style="thin")
)
alignment = Alignment(horizontal="center", vertical="center", wrap_text=True)

# Apply style
style_idx = wb.add_style(font=font, fill=fill, border=border, alignment=alignment)
ws["A1"].value = "Styled Cell"
ws["A1"].style_index = style_idx

wb.save("styles.xlsx")

Insert Images

from pyopenxlsx import Workbook

wb = Workbook()
ws = wb.active

# Insert image at A1, automatically maintaining aspect ratio
# Requires Pillow: pip install pillow
ws.add_image("logo.png", anchor="A1", width=200)

# Or specify exact dimensions
ws.add_image("banner.jpg", anchor="B5", width=400, height=100)

wb.save("images.xlsx")

Comments

Comments are automatically resized to fit their content by default.

from pyopenxlsx import Workbook

wb = Workbook()
ws = wb.active

# Simple or multiline comments - all will auto-size perfectly
ws["A1"].comment = "Short comment"
ws["B2"].comment = "Line 1: High performance\nLine 2: Pythonic API\nLine 3: Auto-sized by default!"

wb.save("comments.xlsx")

---

API Documentation

Module Exports

from pyopenxlsx import (
    # Core Classes
    Workbook, Worksheet, Cell, Range,
    load_workbook, load_workbook_async,
    
    # Style Classes
    Font, Fill, Border, Side, Alignment, Style, Protection,
    
    # Enums & Constants
    XLColor, XLSheetState, XLLineStyle, XLPatternType, XLAlignmentStyle,
    XLProperty, XLUnderlineStyle, XLFontSchemeStyle, XLVerticalAlignRunStyle,
    XLFillType,
)

---

Workbook Class

The top-level container for an Excel file.

Constructor

Workbook(filename: str | None = None, force_overwrite: bool = True)

• filename: Optional. If provided, opens an existing file; otherwise, creates a new workbook.
• force_overwrite: Optional (default: True). If True, overwrites existing files when creating or saving. If False, an exception is raised if the file already exists.

Properties

Property	Type	Description
active	Worksheet | None	Get or set the currently active worksheet.
sheetnames	list[str]	Returns a list of all worksheet names.
properties	DocumentProperties	Access document metadata (title, author, etc.).
styles	XLStyles	Access underlying style object (advanced usage).
workbook	XLWorkbook	Access underlying C++ workbook object (advanced usage).

Methods

Method	Return Type	Description
save(filename=None, force_overwrite=True)	None	Save the workbook. Saves to original path if filename is omitted.
save_async(filename=None, force_overwrite=True)	Coroutine	Asynchronously save the workbook.
close()	None	Close the workbook and release resources.
close_async()	Coroutine	Asynchronously close the workbook.
create_sheet(title=None, index=None)	Worksheet	Create a new worksheet. title defaults to "Sheet1", etc.
create_sheet_async(...)	Coroutine	Asynchronously create a worksheet.
remove(worksheet)	None	Delete the specified worksheet.
remove_async(worksheet)	Coroutine	Asynchronously delete a worksheet.
copy_worksheet(from_worksheet)	Worksheet	Copy a worksheet and return the copy.
copy_worksheet_async(...)	Coroutine	Asynchronously copy a worksheet.
add_style(...)	int	Create a new style and return its index. See below.
add_style_async(...)	Coroutine	Asynchronously create a style.
get_embedded_images()	list[ImageInfo]	Get list of all images embedded in the workbook.
get_image_data(name)	bytes	Get binary data of an embedded image by its name or path.
extract_images(out_dir)	list[str]	Extract all images to a directory. Returns list of file paths.
extract_images_async(...)	Coroutine	Asynchronously extract all images.

add_style Method

def add_style(
    font: Font | int | None = None,
    fill: Fill | int | None = None,
    border: Border | int | None = None,
    alignment: Alignment | None = None,
    number_format: str | int | None = None,
    protection: Protection | None = None,
) -> int:

Returns: A style index (int) that can be assigned to Cell.style_index.

Example:

# Pass all styles via a Style object
from pyopenxlsx import Style, Font, Fill

style = Style(
    font=Font(bold=True),
    fill=Fill(color="C8C8C8"), # Hex color
    number_format="0.00"
)
idx = wb.add_style(style)

---

Worksheet Class

Represents a sheet within an Excel file.

Properties

Property	Type	Description
title	str	Get or set the worksheet name.
index	int	Get or set the worksheet index (0-based).
sheet_state	str	Visibility: "visible", "hidden", "very_hidden".
max_row	int	Returns the maximum row index used.
max_column	int	Returns the maximum column index used.
rows	Iterator	Iterate over all rows with data.
merges	MergeCells	Access merged cells information.
protection	dict	Get worksheet protection status (read-only).

Methods

Method	Return Type	Description
cell(row, column, value=None)	Cell	Get cell by 1-based indices. Optionally set value.
range(address)	Range	Get range by string, e.g., ws.range("A1:C3").
range(start, end)	Range	Get range by endpoints, e.g., ws.range("A1", "C3").
merge_cells(address)	None	Merge cells, e.g., ws.merge_cells("A1:B2").
merge_cells_async(...)	Coroutine	Asynchronously merge cells.
unmerge_cells(address)	None	Unmerge cells.
unmerge_cells_async(...)	Coroutine	Asynchronously unmerge cells.
append(iterable)	None	Append a row of data after the last used row.
append_async(iterable)	Coroutine	Asynchronously append a row.
set_column_format(col, style_idx)	None	Set default style for a column. col can be int or "A".
set_row_format(row, style_idx)	None	Set default style for a row.
column(col)	Column	Get column object for width adjustments.
protect(...)	None	Protect the worksheet.
protect_async(...)	Coroutine	Asynchronously protect the worksheet.
unprotect()	None	Unprotect the worksheet.
unprotect_async()	Coroutine	Asynchronously unprotect.
add_image(...)	None	Insert an image.
add_image_async(...)	Coroutine	Asynchronously insert an image.

add_image Method

def add_image(
    img_path: str,
    anchor: str = "A1",
    width: int | None = None,
    height: int | None = None,
) -> None:

• img_path: Path to image (PNG, JPG, GIF).
• anchor: Top-left cell address.
• width, height: Pixel dimensions. Requires Pillow for auto-detection if not provided.

Magic Methods

Method	Description
__getitem__(key)	Get cell by address: ws["A1"]

---

Cell Class

The fundamental unit of data in Excel.

Properties

Property	Type	Description
value	Any	Get/Set value. Supports str, int, float, bool, datetime.
formula	Formula	Get/Set formula string (without initial =).
style_index	int	Get/Set style index.
style	int	Alias for style_index.
is_date	bool	True if the cell has a date format.
comment	str | None	Get/Set cell comment. Set None to remove.
font	XLFont	Get font object (read-only).
fill	XLFill	Get fill object (read-only).
border	XLBorder	Get border object (read-only).
alignment	XLAlignment	Get alignment object (read-only).

Date Handling

If is_date is True, value automatically returns a Python datetime object.

# Write
ws["A1"].value = datetime(2024, 1, 15)
ws["A1"].style_index = wb.add_style(number_format=14)  # Built-in date format

# Read
print(ws["A1"].value)   # datetime.datetime(2024, 1, 15, 0, 0)
print(ws["A1"].is_date) # True

Formulas

Note: Formulas must be set via the formula property, not value.

# Correct
ws["A3"].formula = "SUM(A1:A2)" 

# Incorrect (treated as string)
ws["A3"].value = "=SUM(A1:A2)"

---

Range Class

Represents a rectangular area of cells.

Properties

Property	Type	Description
address	str	Range address, e.g., "A1:C3".
num_rows	int	Row count.
num_columns	int	Column count.

Methods

Method	Return Type	Description
clear()	None	Clear values in all cells of the range.
clear_async()	Coroutine	Asynchronously clear range.

Iteration

for cell in ws.range("A1:B2"):
    print(cell.value)

---

Style Classes

Font

Font(name="Arial", size=11, bold=False, italic=False, color=None)

Fill

Fill(pattern_type="solid", color=None, background_color=None)

Border

Border(left=Side(), right=Side(), top=Side(), bottom=Side(), diagonal=Side())

Side

Side(style="thin", color=None)

Styles: "thin", "thick", "dashed", "dotted", "double", "hair", "medium", "mediumDashed", "mediumDashDot", "mediumDashDotDot", "slantDashDot"

Alignment

Alignment(horizontal="center", vertical="center", wrap_text=True)

Options: "left", "center", "right", "general", "top", "bottom"

---

DocumentProperties

Accessed via wb.properties. Supports dict-like access.

• Metadata: title, subject, creator, keywords, description, last_modified_by, category, company.

wb.properties["title"] = "My Report"
print(wb.properties["creator"])

---

Column Class

Accessed via ws.column(col_index) or ws.column("A").

Properties

Property	Type	Description
width	float	Get or set the column width.
hidden	bool	Get or set whether the column is hidden.
style_index	int	Get or set the default style index for the column.

---

Formula Class

Accessed via cell.formula.

Properties

Property	Type	Description
text	str	Get or set the formula string.

Methods

Method	Return Type	Description
clear()	None	Remove the formula from the cell.

---

MergeCells Class

Accessed via ws.merges. Represents the collection of merged ranges in a worksheet.

Methods

Method	Return Type	Description
append(reference)	None	Create a merged range (e.g., "A1:B2").
delete(index)	None	Remove a merged range by its index.
find(reference)	int	Find the index of a merged range. Returns -1 if not found.
__len__()	int	Return the number of merged ranges.
__getitem__(index)	XLMergeCell	Get a merged range object by index.
__iter__()	Iterator	Iterate over all merged ranges.
__contains__(ref)	bool	Check if a reference is within any merged range.

---

XLComments Class

Accessed via ws._sheet.comments().

Method	Return Type	Description
add_author(name)	int	Add a new author to the workbook.
set(ref, text, author_id=0)	None	Set comment for a cell reference.
get(ref_or_idx)	str | XLComment	Get comment text or object.
shape(cell_ref)	XLShape	Get the VML shape object for the comment box.
count()	int	Number of comments in the sheet.

---

XLShape Class

Represents the visual properties of a comment box.

Methods

Method	Return Type	Description
style()	XLShapeStyle	Access size, position, and visibility properties.
client_data()	XLShapeClientData	Access Excel-specific anchor and auto-fill data.

---

XLShapeStyle Class

Method	Return Type	Description
set_width(val)	None	Set box width in points.
set_height(val)	None	Set box height in points.
show() / hide()	None	Set comment visibility.

---

XLShapeClientData Class

Method	Return Type	Description
set_anchor(str)	None	Set box position/size using grid coordinates.
set_auto_fill(bool)	None	Enable/disable automatic box sizing.

---

ImageInfo Class

Returned by wb.get_embedded_images().

Attributes

Attribute	Type	Description
name	str	Filename of the image.
path	str	Internal path in the XLSX archive.
extension	str	File extension (e.g., "png").

---

Helper Functions

load_workbook

def load_workbook(filename: str) -> Workbook:
    """Open an existing Excel file."""

load_workbook_async

async def load_workbook_async(filename: str) -> Workbook:
    """Asynchronously open an existing Excel file."""

is_date_format

def is_date_format(format_code: int | str) -> bool:
    """
    Check if a number format code (int) or string represents a date/time format.
    Useful for determining if a cell value should be treated as a datetime.
    """

---

Performance

pyopenxlsx is built for speed. By leveraging the C++ OpenXLSX engine and providing optimized bulk operations, it significantly outperforms pure-Python alternatives.

Benchmarks (pyopenxlsx vs openpyxl)

Scenario	pyopenxlsx	openpyxl	Speedup
Read (20,000 cells)	~7.5ms	~151ms	20x
Write (1,000 cells)	~5ms	~8.4ms	1.7x
Write (50,000 cells)	~178ms	~318ms	1.8x
Bulk Write (50,000 cells)	~80ms	N/A	4.0x
Iteration (20,000 cells)	~86ms	~157ms	1.8x

[!NOTE] Benchmarks were performed on a local development machine using pytest-benchmark. Results may vary based on environment and data complexity. Bulk write uses ws.write_range() with NumPy arrays.

Why is it faster?

1. C++ Foundation: Core operations happen in highly optimized C++.
2. Reduced Object Overhead: pyopenxlsx minimizes the creation of many Python Cell objects during bulk operations.
3. Efficient Memory Mapping: Leverages the memory-efficient design of OpenXLSX.
4. Asynchronous I/O: Key operations are available as non-blocking coroutines to maximize throughput in concurrent applications.

---

Development

Run Tests

# Run all tests
uv run pytest

# With coverage
uv run pytest --cov=src/pyopenxlsx --cov-report=term-missing

License

BSD 3-Clause License. The underlying OpenXLSX library is licensed under the MIT License, and nanobind under a BSD-style license.