Get formula from Excel cell with python xlrd

Update: I have gone and implemented a little library to do exactly what you describe: extracting the cells & dependencies from an Excel spreadsheet and converting them to python code. Code is on github, patches welcome :)

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Just to add that you can always interact with excel using win32com (not very fast but it works). This does allow you to get the formula. A tutorial can be found here [cached copy] and details can be found in this chapter [cached copy].

Essentially you just do:

app.ActiveWorkbook.ActiveSheet.Cells(r,c).Formula

As for building a table of cell dependencies, a tricky thing is parsing the excel expressions. If I remember correctly the Trace code you mentioned does not always do this correctly. The best I have seen is the algorithm by E. W. Bachtal, of which a python implementation is available which works well.

[Dis]claimer: I'm the author/maintainer of xlrd.

The documentation references to formula text are about "name" formulas; read the section "Named references, constants, formulas, and macros" near the start of the docs. These formulas are associated sheet-wide or book-wide to a name; they are not associated with individual cells. Examples: PI maps to =22/7, SALES maps to =Mktng!$A$2:$Z$99. The name-formula decompiler was written to support inspection of the simpler and/or commonly found usages of defined names.

Formulas in general are of several kinds: cell, shared, and array (all associated with a cell, directly or indirectly), name, data validation, and conditional formatting.

Decompiling general formulas from bytecode to text is a "work-in-progress", slowly. Note that supposing it were available, you would then need to parse the text formula to extract the cell references. Parsing Excel formulas correctly is not an easy job; as with HTML, using regexes looks easy but doesn't work. It would be better to extract the references directly from the formula bytecode.

Also note that cell-based formulas can refer to names, and name formulas can refer both to cells and to other names. So it would be necessary to extract both cell and name references from both cell-based and name formulas. It may be useful to you to have info on shared formulas available; otherwise having parsed the following:

B2 =A2
B3 =A3+B2
B4 =A4+B3
B5 =A5+B4
...
B60 =A60+B59

you would need to deduce the similarity between the B3:B60 formulas yourself.

In any case, none of the above is likely to be available any time soon -- xlrd priorities lie elsewhere.

So I know this is a very old post, but I found a decent way of getting the formulas from all the sheets in a workbook as well as having the newly created workbook retain all the formatting.

First step is to save a copy of your .xlsx file as .xls -- Use the .xls as the filename in the code below

Using Python 2.7

from lxml import etree
from StringIO import StringIO
import xlsxwriter
import subprocess
from xlrd import open_workbook
from xlutils.copy import copy
from xlsxwriter.utility import xl_cell_to_rowcol
import os



file_name = '<YOUR-FILE-HERE>'
dir_path = os.path.dirname(os.path.realpath(file_name))

subprocess.call(["unzip",str(file_name+"x"),"-d","file_xml"])


xml_sheet_names = dict()

with open_workbook(file_name,formatting_info=True) as rb:
    wb = copy(rb)
    workbook_names_list = rb.sheet_names()
    for i,name in enumerate(workbook_names_list):
        xml_sheet_names[name] = "sheet"+str(i+1)

sheet_formulas = dict()
for i, k in enumerate(workbook_names_list):
    xmlFile = os.path.join(dir_path,"file_xml/xl/worksheets/{}.xml".format(xml_sheet_names[k]))
    with open(xmlFile) as f:
        xml = f.read()

    tree = etree.parse(StringIO(xml))
    context = etree.iterparse(StringIO(xml))

    sheet_formulas[k] = dict()
    for _, elem in context:
        if elem.tag.split("}")[1]=='f':
            cell_key = elem.getparent().get(key="r")
            cell_formula = elem.text
            sheet_formulas[k][cell_key] = str("="+cell_formula)

sheet_formulas

Structure of Dictionary 'sheet_formulas'

{'Worksheet_Name': {'A1_cell_reference':'cell_formula'}}

Example results:

{u'CY16': {'A1': '=Data!B5',
  'B1': '=Data!B1',
  'B10': '=IFERROR(Data!B12,"")',
  'B11': '=IFERROR(SUM(B9:B10),"")',

It seems that it is impossible now to do what you want with xlrd. You can have a look at this post for the detailed description of why it is so difficult to implement the functionality you need.

Note that the developping team does a great job for support at the python-excel google group.