Excel使用win32com和python

Question

我想知道如何使用win32com客户端为python迭代excel表而不读取整个列。

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.

Answer 2

Have you looked into the openpyxl library? From the documentation:

from openpyxl import load_workbook
wb = load_workbook(filename='file.xlsx')
ws = wb.get_sheet_by_name(name='Sheet1')
columns = ws.columns()

There's also support for iterators and other goodies.

Answer 3

The fastest way would be to use the built in Range functionality through the win32com.client API. However, I'm not a big fan of it. I think the API is confusing and badly documented, and using it isn't very pythonic (but that's just me).

If efficiency is not an issue for you, you can use the excellent xlrd library. Like so:

import xlrd
book = xlrd.open_workbooks('Book1')
sheet = book.sheet_by_name('Sheet1')
sheel.col(1)
sheet.col(2)
# and so on...

That gives you the cell objects. To get pure values, use sheet.col_values (and there are a few other methods that are real nice to work with).

Just remember that xlrd stand for "excel read", so if you want to write to an excel file you need a different library called "xlwt" (which is also pretty good, though less so than xlrd in my opinion).