from aspose.cells import Workbook

#  Create a new workbook
workbook = Workbook()
#  Access the first worksheet
worksheet = workbook.worksheets[0]
#  Access the cell you want to format, for example, cell "A1"
cell = worksheet.cells.get("A1")
#  Set the value of the cell
cell.put_value(12345.6789)
#  Get the cell's style
style = cell.get_style()
#  Set the custom format of the cell to scientific notation
style.custom = "0.00E+00"
#  Apply the style to the cell
cell.set_style(style)
#  Save the workbook to a file
workbook.save("output.xlsx")