How to use Application.FeatureInstall in the xlwings API way

In the xlwings library, the Application object’s FeatureInstall property is a critical component for managing how Microsoft Excel handles the installation of optional features or add-ins that are not initially installed. This property is particularly relevant when your automation script relies on features that may not be available in a standard Excel installation, ensuring that Excel can dynamically install them as needed without manual intervention. Understanding and utilizing FeatureInstall can enhance the robustness of your xlwings scripts, especially in environments where Excel configurations vary.

Functionality:
The FeatureInstall property determines the method Excel uses to install features when they are required by a command or operation but are not currently installed. This is essential for maintaining seamless automation, as it prevents errors or interruptions that could occur if a needed feature is missing. By setting this property appropriately, you can control whether Excel prompts the user, installs features automatically, or disables the feature installation process altogether.

Syntax:
In xlwings, you can access the FeatureInstall property through the app object, which represents the Excel application. The syntax is straightforward:

app.api.FeatureInstall

This property is both readable and writable, allowing you to retrieve or set its value. The value corresponds to an enumeration that defines the installation behavior. In xlwings, you typically use integer constants from the msoFeatureInstall enumeration, which is part of the Microsoft Office object model. The key values are:

Constant Name (VBA)	xlwings Value	Description
msoFeatureInstallNone	0	Disables feature installation; Excel will not install missing features and may fail if they are required.
msoFeatureInstallOnDemand	1	Prompts the user to install features when needed, which is the default behavior in many Excel setups.
msoFeatureInstallOnDemandWithUI	2	Similar to on-demand but may include additional user interface elements during installation.
msoFeatureInstallOnDemandWithUI	2	Similar to on-demand but may include additional user interface elements during installation.

To set the property, assign one of these integer values to app.api.FeatureInstall. For example, to set it to install features automatically without user prompts, you would use msoFeatureInstallOnDemand (value 1), but note that the actual behavior can depend on Excel’s configuration and user permissions.

Code Examples:
Here are practical examples of using the FeatureInstall property in xlwings:

1. Retrieving the Current FeatureInstall Setting:
   This code checks how Excel is currently configured to handle feature installation.

import xlwings as xw
app = xw.App(visible=False) # Start Excel in the background
current_setting = app.api.FeatureInstall
print(f"Current FeatureInstall setting: {current_setting}")
app.quit()

Output might be 1, indicating on-demand installation.

2. Setting FeatureInstall to Disable Installation:
   This example configures Excel to not install any missing features, which can be useful in controlled environments where all features are pre-installed.

import xlwings as xw
app = xw.App(visible=False)
app.api.FeatureInstall = 0 # msoFeatureInstallNone
print("Feature installation disabled.")
app.quit()

3. Enabling On-Demand Installation with UI:
   This sets Excel to prompt users for installation when features are missing, providing a balance between automation and user control.

import xlwings as xw
app = xw.App(visible=True) # Make Excel visible to see prompts
app.api.FeatureInstall = 2 # msoFeatureInstallOnDemandWithUI
print("On-demand feature installation with UI enabled.")
# Perform operations that might require additional features
app.quit()

4. Integrating with a Script to Handle Missing Features:
   In a more complex scenario, you might adjust FeatureInstall based on the script’s needs. For instance, if your automation uses advanced charting tools that may not be installed, you could set it to on-demand to ensure they are available.

import xlwings as xw
app = xw.App(visible=False)
app.api.FeatureInstall = 1 # msoFeatureInstallOnDemand
workbook = app.books.open('data.xlsx')
# Add a chart that might require additional features
sheet = workbook.sheets['Sheet1']
chart = sheet.charts.add()
chart.set_source_data(sheet.range('A1:B10'))
chart.chart_type = 'xlColumnClustered'
workbook.save()
app.quit()