If you want to automate CATIA V5 with Python you need Pywin32 and Python for Windows. Python is free software and you can develop professional applications with all advantages of Python for CATIA V5. And you can deploy your applications as a standard Windows executable what you cannot do with the builtin Macro language VB.

For developing a small application which interacts to CATIA V5 you only have to download Python for Windows and Pywin32 from Marc Hammond (please see the Download section). CATIA V5 must be also installed and should be running when testing the application.

If you have done that you can test it with this source code:

 
import win32com.client
a = win32com.client.Dispatch('catia.application')
doc=a.ActiveDocument.Product
for i in range(doc.Products.Count):
    print 'Part Number:', doc.Products.Item(i+1).PartNumber

It prints out the part names of a loaded CATProduct. Other examples can be found in the script collection.

Hint: You can automate DMU Navigator as well as CATIA V5 with this Dispatch string:

a = win32com.client.Dispatch('DMU.application')

Important notes:

If you want to use early binding for the CATIA V5 object libraries you can use the Makepy utility from Pythonwin. After that every object and its methods will be usable from the pulldown menu while typing and you can have a performance advantage. You should use makepy for every object library which you want to use e.g. "ProductStructure Object Library" for working with CATProducts). Not for the "CATIA V5 Interfaces Objekt Library"!

But if you have done that stupidly, every application which uses early binding for the "CATIA V5 Interfaces Objekt Library" will not work ! A workaround is not to use makepy for the "CATIA V5 Interfaces Objekt Library" or use explicit late binding "(import win32com.client.dynamic as the first line).

For starting developing applications with Python for CATIA V5 you should use the manual V5Automation.chm which you can find in the bin-directory of CATIA V5. You will see that you can develop Python applications in the same way like VB with the builtin VB editor.

If you have problems to access the COM Interface from CATIA V5 (eg. no object libraries from CATIA V5 in makepy) please check whether CATIA V5 was registrated as a COM server. If not you can do that with cnext.exe /regserver in the CATIA V5 bin-directory. Then everything should work well...

More information for developing with Python for COM applications with Pywin32 you can find in this excellent book. A whole example Chapter about COM Programming with Python/Pywin32 can be found here.

Python Programming on Win32
by Mark Hammond, Andy Robinson
ISBN: 1-56592-621-8
652 pages. January 2000.