Thanks runrig!

My issue is that except for the four columns from A-D (which are string), all the other ones are numbers. And since I am populating these cells from a csv file, I have automated it to be printed with write() method for each cell.

Hence I was trying to set a format for those 4 columns, but you pointed it right, 'Text' cannot be a number format indeed.
<\br> For now, I have considered these as special cases and using regex i identify the tokens with such formats (like 801495E40) and print them using write_string() method.
<\br> Thanks for the help!