I corrupted a workbook by setting a bad validation range
*Created originally on Bitbucket by [zvirack (Zvi Rackover)](https://bitbucket.org/%7Bb9eff355-63bd-4013-8404-c0cf549c0831%7D/)* Not sure if this is a user error, a bug or a feature request. I am using the latest released package. The following code corrupted my workbook. The problem was that the column letters were in lower case. ``` #!python decimal = DataValidation(type="decimal") decimal.ranges.append("c2:e14") ws.add(decimal) ... Save the workbook ``` Next time i loaded the workbook using openpyxl, an exception was raised after the regex which expects upper-case range letters failed. So if this is not a user error, i suggest that openpyxl will either fail when entering a range which does not match the regex or use a more robust regex allowing lower-case column letters. Thanks
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