Prepare simple table with spacing based on content

def _tabulate(rows, headers, spacing=5):
    """Prepare simple table with spacing based on content"""
    if len(rows) == 0:
        return "None\n"
    assert len(rows[0]) == len(headers)
    count = len(rows[0])
    widths = [0 for _ in range(count)]
    rows = [headers] + rows

    for row in rows:
        for index, field in enumerate(row):
            if len(str(field)) > widths[index]:
                widths[index] = len(str(field))

    output = ""
    for row in rows:
        for index, field in enumerate(row):
            field = str(field)
            output += field + (widths[index] - len(field) + spacing) * " "
        output += "\n"
    return output