How to use Range.CalculateRowMajorOrder in the xlwings API way

The CalculateRowMajorOrder member of the Range object in Excel is a property that controls the calculation order for formulas within the specified range when using the row-major calculation method. In Excel, calculation can proceed in row-major order (left to right, then top to bottom) or column-major order (top to bottom, then left to right). This property is particularly useful in scenarios where formula dependencies are arranged in a way that row-wise calculation improves performance or ensures correct results, such as in financial models or data tables with horizontal dependencies. It allows developers to programmatically set or check the calculation direction for a specific range, overriding the default application-wide setting.

In the xlwings API, which provides a Pythonic interface to Excel’s object model, the CalculateRowMajorOrder property is accessed through a Range object. The syntax for using it is straightforward, as it is a read/write property that accepts and returns a Boolean value. When set to True, Excel calculates the formulas in the range using row-major order. When set to False, it uses column-major order, which is Excel’s default behavior if not specified otherwise. This property can be applied to any Range object, from a single cell to a larger block of cells, enabling fine-tuned control over calculation logic.

The xlwings API call format for CalculateRowMajorOrder is as follows:

• To get the current value: range_object.calculate_row_major_order
• To set the value: range_object.calculate_row_major_order = True or range_object.calculate_row_major_order = False

Here, range_object is an instance of xlwings’ Range class, typically obtained through methods like ws.range() where ws is a Sheet object. The property does not take additional parameters; it simply reflects or alters the calculation order setting. In terms of usage, it is often combined with the calculate() method to trigger a recalculation after setting the order. Note that this property might not be available in all Excel versions or contexts, so it’s advisable to check compatibility, especially with older Excel editions.

For example, consider a scenario where you have a worksheet with formulas in cells A1:C3 that depend horizontally (e.g., cell B1 references A1, and C1 references B1). To ensure these formulas are calculated in the correct left-to-right sequence, you can set CalculateRowMajorOrder to True for that range. Below is an xlwings API code instance demonstrating this:

import xlwings as xw

# Connect to an existing Excel workbook and sheet
wb = xw.Book('example.xlsx')
ws = wb.sheets['Sheet1']

# Define the range A1:C3
target_range = ws.range('A1:C3')

# Set calculation order to row-major for this range
target_range.calculate_row_major_order = True

# Trigger calculation to apply the new order
target_range.calculate()

# Check the current setting
current_order = target_range.calculate_row_major_order
print(f"CalculateRowMajorOrder is set to: {current_order}")

# Optionally, revert to column-major order
target_range.calculate_row_major_order = False
target_range.calculate()

# Close the workbook (optional, based on workflow)
wb.save()
wb.close()