Python/win32com - Check if Program is Open

Question

I have a script where I use win32com to interact with a COM service. It works as intended when the program is already open. I connect to it using win32com.client.dynamic.Dispatch, then interact with a document that should already be open. Assuming the program is already open, I can easily check if a document is open, but I'm not sure how to check if the program is already open or not. When I use the Dispatch mentioned, it just starts the program if it isn't already open, which is not what I want.

Solution

try win32com.client.GetActiveObject() method. This is what I use in some convenience functions I've written, this one for Excel:

def Excel(visible=True):
    '''Get running Excel instance if possible, else 
    return new instance. 
    '''
    try: 
        excel = win32com.client.GetActiveObject("Excel.Application")
        print("Running Excel instance found, returning object")

    except:
        excel = new_Excel(visible=visible)
        print("No running Excel instances, returning new instance")

    else:
        if not excel.Workbooks.Count:
            excel.Workbooks.Add(1)
        excel.Visible = visible

    return excel

new_Excel is just another convenience function for opening new instances of the Excel application object.

Comments

[frakman1]

How would you handle the case when Excel isn't installed? If I use excel = win32.Dispatch('excel.application'), it crashes if Excel isn't installed: pywintypes.com_error: (-2147221005, 'Invalid class string', None, None) How do I gracefully check first before trying to send the Dispatch?