openpyxl - FutureWarning: The behavior of this method will change in future versions. Use specific 'len(elem)' or 'elem is not None' test instead

Question

I'm getting a warning when loading an xlsm file using openpyxl for python, then saving/closing it after I add some data to specific 7 cells in a specific sheet. The issue is that I'm getting a "FutureWarning" that I have no idea what it is about. I've searched for this for some time now and have not been able to decipher.

I'm suspecting that the wb.save() method is what's triggering this warning as it doesn't show up when I comment this specific line up.

Does anyone know what this is?

CODE

wb = openpyxl.load_workbook(filename=directory_path.xlsm, keep_vba=True)
ws = wb['sheetname']
ws.cell(row1, col1).value = ### (some number)
ws.cell(row2, col2).value = ### (some number)
ws.cell(row3, col3).value = ### (some number)
ws.cell(row4, col4).value = ### (some number)
ws.cell(row5, col5).value = ### (some number)
ws.cell(row6, col6).value = ### (some number)
ws.cell(row7, col7).value = ### (some number)
wb.save(directory_path.xlsm)
wb.close()

WARNING MESSAGE

C:\Users\...\Anaconda3\lib\site-packages\openpyxl\comments\shape_writer.py:75: FutureWarning: The behavior of this method will change in future versions. Use specific 'len(elem)' or 'elem is not None' test instead.
  if not shape_types:

This actually is not a error, but a warning as your prompt shows. — user2906838, Aug 02 '18 at 04:16
thanks, I'm aware and the typo was fixed in the posting. Do you know what that warning means though? — akondo, Aug 02 '18 at 04:24
as mentioned in the post, I'm suspecting it's happening at the penultimum line (at the .save() method). The output doesn't give any sort of traceback. Only the one line warning in the post — akondo, Aug 02 '18 at 04:43

score 5 · Accepted Answer · answered Aug 02 '18 at 04:55

Openpyxl seems to be using an older version of lxml. It is a warning in your version of lxml.

Line 73-76 of the shape_writer source code are:

# check whether comments shape type already exists
shape_types = root.find("{%s}shapetype[@id='_x0000_t202']" % vmlns)
if not shape_types:
    self.add_comment_shapetype(root)

The issue is the if not shape_types:. root.find() is a call to lxml. The documentation for lxml says:

Prior to ElementTree 1.3 and lxml 2.0, you could also check the truth value of an Element to see if it has children, i.e. if the list of children is empty:

if root:   # this no longer works!
    print("The root element has children")

This is no longer supported as people tend to expect that a "something" evaluates to True and expect Elements to be "something", may they have children or not. So, many users find it surprising that any Element would evaluate to False in an if-statement like the above. Instead, use len(element), which is both more explicit and less error prone.

Thanks Alex! Does this mean that I should not use wb.save() to avoid any post-deployment complication in the future as I develop my program? Is there an alternative way of saving the changes made to the loaded workbook? — akondo, Aug 03 '18 at 03:05
It's fine - for now. The Openpxyl team need to update their code. It's a good chance to contribute to open source... — Alex Taylor, Aug 03 '18 at 03:41
As to the unexpected behavior of ElementTree I was was among the ones fooled by it once. As to the matter at hand, if you'd like to suppress it [see this comment of mine](https://stackoverflow.com/questions/2828953/silence-the-stdout-of-a-function-in-python-without-trashing-sys-stdout-and-resto#comment107567752_28321717) — z33k, Mar 22 '20 at 11:02

openpyxl - FutureWarning: The behavior of this method will change in future versions. Use specific 'len(elem)' or 'elem is not None' test instead

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