How to save an excel using pywin32?

I am trying to save an excel file generated by another application that is open. i.e the excel application is in the foreground. This file has some data and it needs to be saved i.e written into the disk.

In other words, I need to do an operation like File->SaveAs.

Steps to reproduce:

Open an Excel Application. This will be shown as Book1 - Excel in the title by default
Write this code and run

import win32com.client as win32

app = win32.gencache.EnsureDispatch('Excel.Application')
app.Workbooks(1).SaveAs(r"C:\Users\test\Desktop\test.xlsx")
app.Application.Quit()

Error -

Traceback (most recent call last):
  File "c:/Users/test/Downloads/automate_excel.py", line 6, in <module>
    ti = disp._oleobj_.GetTypeInfo()
pywintypes.com_error: (-2147418111, 'Call was rejected by callee.', None, None)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:/Users/test/Downloads/automate_excel.py", line 6, in <module>
    app = win32.gencache.EnsureDispatch('Excel.Application')
  File "C:\Users\test\AppData\Local\Programs\Python\Python38\lib\site-packages\win32com\client\gencache.py", line 633, in EnsureDispatch
    raise TypeError(
TypeError: This COM object can not automate the makepy process - please run makepy manually for this object

Solution

This is the version that worked for me based on @scotscotmcc's answer. The issue was with the cell which was in edit mode while I was running the program. Make sure you hit enter in the current cell and come out of the edit mode in excel.

import win32com.client as win32
import random
xl = win32.Dispatch('Excel.Application')
wb = xl.Workbooks['Book1']
wb.SaveAs(r"C:\Users\...\Desktop\Form"+str(random.randint(0,1000))+".xlsx")
wb.Close()
xl.Quit()