def get_max_sheet(book):
    """
    Get the sheet in the workbook with the most rows of data
    :param book: An xlrd book object
    :return: Returns an xlrd sheet object
    """
    row_counts = [s.nrows for s in book.sheets()]  # list of row counts for each sheet
    max_sheet_index = row_counts.index(max(row_counts))  # find list index for largest sheet
    sheet = book.sheet_by_index(max_sheet_index)  # return the sheet with the greatest number of rows
    return sheet