error: unpack requires a string argument of length 8 - python-2.7

Question

I was running my script and I stumbled upon on this error
WARNING *** file size (24627) not 512 + multiple of sector size (512)
WARNING *** OLE2 inconsistency: SSCS size is 0 but SSAT size is non-zero
Traceback (most recent call last):
File "C:\Email Attachments\whatever.py", line 20, in <module>
main()
File "C:\Email Attachments\whatever.py", line 17, in main
csv_from_excel()
File "C:\Email Attachments\whatever.py", line 7, in csv_from_excel
sh = wb.sheet_by_name('B2B_REP_YLD_100_D_SQ.rpt')
File "C:\Python27\lib\site-packages\xlrd\book.py", line 442, in sheet_by_name
return self.sheet_by_index(sheetx)
File "C:\Python27\lib\site-packages\xlrd\book.py", line 432, in sheet_by_index
return self._sheet_list[sheetx] or self.get_sheet(sheetx)
File "C:\Python27\lib\site-packages\xlrd\book.py", line 696, in get_sheet
sh.read(self)
File "C:\Python27\lib\site-packages\xlrd\sheet.py", line 1055, in read
dim_tuple = local_unpack('<ixxH', data[4:12])
error: unpack requires a string argument of length 8
I was trying to process this excel file.
https://drive.google.com/file/d/0B12NevhOGQGRMkRVdExuYjFveDQ/edit?usp=sharing
One solution that I found is that I have to open manually the spreadsheet, save it, then close it before I run my script of converting .xls to .csv. I find this solution a bit cumbersome and clunky.
This kind of spreadsheet is saved daily in my drive via an Outlook Macro. Unprocessed data is increasing that's why I turned into scripting to ease the job.

Answer 1

Who made the Outlook macro that's dumping this file? xlrd uses byte level unpacking to read in the Excel file, and is failing to read a field in this excel file. There are ways to follow where its failing, but none to automatically recover from this type of error.
The erroneous data seems to be at data[4:12] of a specific frame (we'll see later), which should be a bytestring that's parsed as such:
one integer (i)
2 pad bytes (xx)
unsigned short 2 byte integer (H).
You can set xlrd to DEBUG mode, which will show you which bytes its parsing, and exactly where in the file there is an error:
import xlrd
xlrd.DEBUG = 2
workbook = xlrd.open_workbook(u'/home/sparker/Downloads/20131117_040934_B2B_REP_YLD_100_D_LT.xls')
Here's the results, slightly trimmed down for the sake of SO:
parse_globals: record code is 0x0293
parse_globals: record code is 0x0293
parse_globals: record code is 0x0085
CODEPAGE: codepage 1200 -> encoding 'utf_16_le'
BOUNDSHEET: bv=80 data '\xfd\x04\x00\x00\x00\x00\x18\x00B2B_REP_YLD_100_D_SQ.rpt'
BOUNDSHEET: inx=0 vis=0 sheet_name=u'B2B_REP_YLD_100_D_SQ.rpt' abs_posn=1277 sheet_type=0x00
parse_globals: record code is 0x000a
GET_SHEETS: [u'B2B_REP_YLD_100_D_SQ.rpt'] [1277]
GET_SHEETS: sheetno = 0 [u'B2B_REP_YLD_100_D_SQ.rpt'] [1277]
reqd: 0x0010
getbof(): data='\x00\x06\x10\x00\xbb\r\xcc\x07\x00\x00\x00\x00\x06\x00\x00\x00'
getbof(): op=0x0809 version2=0x0600 streamtype=0x0010
getbof(): BOF found at offset 1277; savpos=1277
BOF: op=0x0809 vers=0x0600 stream=0x0010 buildid=3515 buildyr=1996 -> BIFF80
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "build/bdist.macosx-10.4-x86_64/egg/xlrd/__init__.py", line 457, in open_workbook
File "build/bdist.macosx-10.4-x86_64/egg/xlrd/__init__.py", line 1007, in get_sheets
File "build/bdist.macosx-10.4-x86_64/egg/xlrd/__init__.py", line 998, in get_sheet
File "build/bdist.macosx-10.4-x86_64/egg/xlrd/sheet.py", line 864, in read
struct.error: unpack requires a string argument of length 8
Specifically, you can see that it parses the name of the workbook named u'B2B_REP_YLD_100_D_SQ.rpt.
Lets check the source code. The traceback throws an error here where we can see from the parent loop that we're trying to parse the XL_DIMENSION and XL_DIMENSION2 values. These directly correspond to the shape of the Excel Sheet.
And that's where there's a problem in your workbook. It's not being made correctly. So, back to my original question, who made the excel macro? It needs to be fixed. But that's for another SO question, some other time.