Python Programming On Win32

Early-Bound Automation

The PythonCOM package can also use early binding for COM objects. This means that the information about the object model (i.e., the properties and methods available for an object) is determined in advance from type information supplied by the object.

Python uses the MakePy utility to support early-bound automation. MakePy is a utility written in Python that uses a COM type library to generate Python source code supporting the interface. Once you use the MakePy utility, early binding for the objects is automatically supported; there’s no need to do anything special to take advantage of the early binding.

There are a number of good reasons to use MakePy:

• The Python interface to automation objects is faster for objects supported by a MakePy module.

• Any constants defined by the type library are made available to the Python program. We discuss COM constants in more detail later in the chapter.

• There is much better support for advanced parameter types, specifically, parameters declared by COM as BYREF can be used only with MakePy-supported objects. We discuss passing parameters later in the chapter.

And there are a few reasons to avoid MakePy:

• Using a MakePy-supported object means you must run MakePy before code that requires it can be used. Although this step can be automated (i.e., made part of your program), you may choose to avoid it.

• The MakePy-generated files can be huge. The file generated for Microsoft Excel is around 800 KB, a large Python source file by anyone’s ...