def last_col_first(df):
    """
    Reorders the columns of a pandas DataFrame.
    Brings the last column to the start (left) of the table.
    Leaves the other columns in their original order.
    df  :   a padas DataFrame.
    """
    cols = df.columns.tolist()
    cols = cols[-1:] + cols[:-1]
    # df = df[cols]
    df = df.loc[:, cols]
    return df