How to use Application.Ready in the xlwings API way

The Ready member of the Application object in Excel is a property that indicates whether Excel has completed any pending calculations, data refreshes, or operations, and is ready to accept user input or further automation commands. In the context of automation via xlwings, this property is particularly useful when you need to ensure that Excel is in a stable, idle state before proceeding with subsequent operations, such as reading calculated values, saving workbooks, or executing macros. This can help prevent errors or race conditions in scripts that interact with a live Excel instance.

In xlwings, you access the Ready property through the app object, which represents the Excel application. The property is read-only and returns a Boolean value: True if Excel is ready, and False otherwise. The syntax for accessing it is straightforward:

app.api.Ready

Here, app is your xlwings App instance, and .api provides direct access to the underlying Excel object model, including the Application object and its members. The Ready property does not take any parameters. It’s a simple check that you can use in conditional statements or loops to pause execution until Excel is ready.

A common use case is to wait for Excel to finish calculating after changing cell values or formulas, especially in workbooks with complex calculations or external data connections. Instead of using arbitrary time delays (e.g., time.sleep()), which can be inefficient or unreliable, polling the Ready property ensures that your script proceeds only when Excel is truly idle. However, note that in some scenarios, such as when Excel is displaying a modal dialog (like a message box), the Ready property might return False indefinitely, so it’s best used in controlled environments where such dialogs are avoided.

Below is a code example that demonstrates how to use the Ready property in xlwings. This script opens an Excel workbook, performs an operation that triggers calculations, and waits for Excel to be ready before reading a result:

import xlwings as xw

# Start or connect to an Excel application
app = xw.App(visible=True) # Set visible=False for background operation

# Open a workbook (replace with your file path)
wb = app.books.open('example.xlsx')
sheet = wb.sheets['Sheet1']

# Change a cell value that triggers calculations, e.g., a formula dependency
sheet.range('A1').value = 100

# Check if Excel is ready; poll in a loop if necessary
while not app.api.Ready:
    # You can add a short sleep to avoid excessive CPU usage, but keep it minimal
import time
    time.sleep(0.1) # Sleep for 100 milliseconds between checks

# Once ready, read a calculated value from another cell
result = sheet.range('B1').value
print(f"Calculated result: {result}")

# Save and close
wb.save()
wb.close()
app.quit()