How to use Application.Watches in the xlwings API way

The Watches member of the Excel Application object in xlwings provides a programmatic way to manage and interact with the Watch Window feature in Excel. The Watch Window is a debugging and monitoring tool that allows users to track the values of specific cells or formulas across different worksheets and workbooks, updating in real-time as changes occur. Through the Watches collection in xlwings, developers can add, delete, or modify watches dynamically, enabling automation of data validation, error checking, or performance monitoring in complex Excel models.

In xlwings, the Watches collection is accessed via the Application object. The syntax for referencing it is straightforward: app.api.Watches, where app is an instance of the xlwings App class representing the Excel application. This returns a COM object that mirrors the VBA Watches collection, allowing access to its methods and properties. Key methods include Add, which creates a new watch, and Delete, which removes an existing one. The Add method requires parameters such as the source (a Range object) and optional arguments like the sheet name or workbook, which can be specified using xlwings range objects or Excel range addresses as strings. For example, to add a watch for cell A1 on the active sheet, you would use app.api.Watches.Add(app.range('A1').api). Properties like Count can be used to iterate through existing watches, and each watch item in the collection has properties such as Formula (the cell reference or formula being watched) and Value (the current value).

Here is a code example demonstrating the use of the Watches member in xlwings:

import xlwings as xw

# Connect to the active Excel instance or start a new one
app = xw.apps.active

# Add a watch for cell B5 on the first sheet of the active workbook
sheet = app.books.active.sheets[0]
watch_range = sheet.range('B5')
app.api.Watches.Add(watch_range.api)

# Check the number of watches currently in the Watch Window
watch_count = app.api.Watches.Count
print(f"Number of watches: {watch_count}")

# List all watches and their details
for i in range(1, watch_count + 1):
    watch = app.api.Watches.Item(i)
    print(f"Watch {i}: Formula = {watch.Formula}, Value = {watch.Value}")

# Delete a specific watch by index (e.g., the first watch)
if watch_count > 0:
    app.api.Watches.Item(1).Delete()

# Alternatively, delete all watches
app.api.Watches.Delete()