Python Programming On Win32

Adding a Chart

Adding a chart proved quite a challenge. There’s a promising-sounding Microsoft Chart COM library, but it turned out not to allow automation in the same way as Word and Excel. Finally we decided to just make up an Excel chart, which is probably easier for users as well. A spreadsheet and chart can be easily designed by hand, and you can update the numbers, recalculate, and save using the tools in Chapter 9. However, the problem remained of how to add a new object and position it correctly within the document. The problem took us several hours to solve and into some dark and surprising corners of Word’s object model. Since the same techniques apply to positioning any OLE object or even a bitmap from a file, it’s worth going over the objects in question.

A little reading of the Word help file turned up the Shapes collection, which claims to represent all the nontext objects in the document: OLE objects, WordArt, graphic files, text boxes, and Word drawing objects. The collection has a number of Add methods, including one called AddOLEObject . AddOLEObject has a multitude of arguments, but allows you to specify a class and a file; thus Document.Shapes.Add(ClassType='Excel.Chart',FileName='mychart.xls') inserts the chart somewhere in the document and creates a new Shape object to refer to it. The Shapes collection lives somewhere called the drawing layer, which floats above each page and isn’t part of the document. The Shape object has an Anchor property that should ...