It's possible, but you need to know what file you will be reading to know what libs to use. You'll need to decode it from base64 and probably save it into a StringIO.

You can make a method that you then execute on button click and it reads the file from field. 

from xlrd import open_workbook
import base64
import StringIO

class ExcelImport(models.TransientModel):
    _name = 'excell.import.wizard'

    excel_file_for_import = fields.Binary(string='File for upload')

    def import_data_form_file(self):
        try:
            inputx = StringIO.StringIO()
            inputx.write(base64.decodestring(self.excel_file_for_import))
            book = open_workbook(file_contents=inputx.getvalue())
        except TypeError as e:
            raise ValidationError(u'ERROR: {}'.format(e))
        sheet = book.sheets()[0]

        for i in range(sheet.nrows):
            if i == 0:
                continue
            if i == 1:
                name = sheet.cell(i, 0).value
                vat = sheet.cell(i, 5).value