How to define last row in xlsxwriter while using add_chart - python-2.7

Question

I running a script to take rows and columns from a worksheet and use it to make charts. The problem that I am running into is that since the rows in the MSEXCEL sheet are changing, I want to add the last row in the add_series argument so that it will always take the limit of the chart data from row 2 till the last row.
This is the code that I am using currently (that I want to change):
chart1 = workbook.add_chart({'type': 'column'})
chart1.add_series({
'values': "='Sheet1'!$B$2:$B$126",
'categories': "='Sheet1'!$A$2:$A$126",
'data_labels': {'value': False, 'categories': False, 'series': False}
})
I have modified the above code to the following, but now the charts are not getting any data whatsoever.
chart1 = workbook.add_chart({'type': 'column'})
chart1.add_series({
'values': "='Sheet1'!$B$2:($B$ + str(last_row_number + 1)",
'categories': "='Sheet1'!$A$2:($A$ + str(last_row_number + 1)",
'data_labels': {'value': False, 'categories': True, 'series': False}
last_row_number in this case is a variable [<type 'int'>] calculated by enumerating through the worksheet column.
Thanks in advance.

Answer 1

Almost every interface in XlsxWriter supports (row, col) notation as well as A1 range notation.
In the case of add_series() you can use lists like [sheetname, first_row, first_col, last_row, last_col]:
chart.add_series({
'categories': ['Sheet1', 1, 0, 125, 0],
'values': ['Sheet1', 1, 1, 125, 1],
# ...
})
# Or:
last_row = 125
chart.add_series({
'categories': ['Sheet1', 1, 0, last_row, 0],
'values': ['Sheet1', 1, 1, last_row, 1],
# ...
})
See the docs for add_series().