There are a number of resources available on the Developer Zone for using Geomatica in Python - https://dev.pcigeomatics.com/developer-zone. The Getting Started tutorial is helpful for new users - https://support.pcigeomatics.com/hc/en-us/articles/207601873-Getting-Started-with-Geomatica-and-Python
You would use the Geomatica FEXPORT algorithm to export from Geomatica PIX format to any other supported format. More information about the FEXPORT algorithm is available in the online help - https://www.pcigeomatics.com/geomatica-help/references/pciFunction_r/python/P_fexport.html.
The following tutorial outlines how to create a batch script in Python, although you would need to adjust this script to run FEXPORT instead of PANSHARP - https://support.pcigeomatics.com/hc/en-us/articles/207707003-Creating-a-Batch-Workflow-Pansharpening-