Excel using win32com and python

Question

I wanted to know how to read an entire column without iterating from an excel sheet using win32com client for python.

Answer 1

You can read an entire column without iterating from a sheet using the Range collection. You should never use Cells if performacne is any concern. Python uses the win32com module to interact with the Excel COM library. Whenever you use Python and COM (Excel, PowerPoint, Acess, ADODB, etc.) one of your biggest performance constraints will be IO between COM and Python. With the Range method you only make one COM method call while with Cells you make one for each row. This would also be faster if you were doing the same in VBA or .NET

In the following test I created a worksheet with 10 random characters in cells A1 through A2000. I then extracted these values into lists using both Range and Cells.

import win32com.client
app = win32com.client.Dispatch("Excel.Application")
s = app.ActiveWorkbook.Sheets(1)

def GetValuesByCells():
    startTime = time.time()
    vals = [s.Cells(r,1).Value for r in range(1,2001)]
    return time.time() - startTime

def GetValuesByRange():
    startTime = time.time()
    vals = [v[0] for v in s.Range('A1:A2000').Value]
    return time.time() - startTime

>>> GetValuesByRange()
0.03600001335144043

>>> GetValuesByCells()
5.27400016784668

In this case Range is 2 orders of magnitude faster (146x) faster than Cells. Note that the Range method returns a 2D list where each inner list is a row. The list iteration transposes vals into a 2D list where the inner list is a column.