OpenPyXl不存储空单元格(表示没有值，字体，边框等的空单元).如果从工作表中获得一个单元格，它将动态创建一个具有None值的新的空单元格.

OpenPyXl doesn’t store empty cells (empty means without value, font, border, and so on). If you get a cell from a worksheet, it dynamically creates a new empty cell with a None value.

Worksheet.iter_rows()的当前实现(v2.4.0)使用Worksheet.cell()方法，该方法调用没有 value 的Cell()构造函数.

The current implementation (v2.4.0) of Worksheet.iter_rows() use Worksheet.cell() method which calls Cell() constructor with no value.

您需要更改代码以处理空"单元格:

You need to change your code to handle "empty" cells:

for rownum in sh.iter_rows():
    values = [(u"" if cell.value is None else unicode(cell.value))
              for cell in rownum]
    wr.writerow([value.encode('ascii', 'ignore') for value in rownum])

注意:由于可能是Windows用户将数据导出到CSV文件，因此您可以选择更有用的编码，例如:cp1252.

Note: since you export your data to a CSV file for, presumably Windows users, you may choose a more useful encoding like: cp1252.