Debugging Python in Maya
Cyrille Fauvel - ADN
About the Presenter
Cyrille Fauvel - Autodesk Developer Network
Cyrille is a member of the M&E workgroup of the Autodesk Developer Network (ADN)
team, providing developer support, training, and conference presentations on
AutoCAD, RealDWG, Inventor, Maya, 3ds Max, FBX API, and many others.
He joined Autodesk in 1994 as an AutoCAD developer based in Switzerland and
California, USA. Later moved to the Developer Support group, and Consulting division.
Cyrille graduated in Mechanics and Electronics in France, worked as a teacher and C++
developer for a 3rd party developer on AutoCAD. He is fluent in six programming
languages, tries to learn Japanese which turns out to be more difficult than learning
English, has two kids, plays the guitar and piano, likes reading, love sailing on oceans,
sports, and especially hand-ball.
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Agenda
• Maya and Python
• Maya integration and Python development
• Debugging Python in Maya
– What benefits? What risks?
• Exploring various solutions (with demos)
• Q&A
Maya and Python
• Introduced in the 8.5 release
– Scripting & API
– For scripting, see PyMEL (more pythonic)
• Adoption in 2010/2011 releases
– Maya engineering team continues to improve
Python support in Maya releases
Maya Python Scripting
• Wraps MEL
• Embedded UI
– Color syntax
– Automatically saved
– Automatically reparsed
– No intellisense
– No debugger
Maya Python API
• C++ wrappers
• OpenMaya & Maya
– Works like C++ plug-ins /
applications
– Difficult to debug
Debugging Python in Maya
What benefits?
What risks?
Python internal
• Pythons dictionaries
– Python loads module only once
– References are saved into internal Dictionaries
– I.e.: imp.load_module and
__builtin__.__import__
Risks
• If not using reload(), code is not reparsed
• Python variables may be initialized already
– Internal and application variables
• Maya may have references set already
– Nodes or UI
Not using a debugger
• Use print() ?
– Painful and cumbersome
– Slow process
– No control on execution
• Needs overriding __str__() for better
Runtime Information
Using a debugger
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Conditional Breakpoint
Inspect variables / Evaluating some expression
Code changes / Alter debug data values
Exception traceback reporting
Call stack
Remote debugging
Solutions available
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Python pdb debugger
Winpdb http://winpdb.org/docs/embedded-debugging/
Eclipse and pydev http://pydev.org/
Wingware IDE http://www.wingware.com/
Python pdb debugger
• Available in all Python distribution
import pdb
pdb.run(“…”)
• Maya Script editor does not support pdb
– Requires you to redirect the sys.stdin and
sys.stdout in order to control pdb i/o
• Not really a solution for plug-ins
Winpdb
• Light debugger and IDE
– But free
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Breakpoints
Callstack
Inspect values
Exceptions
Eclipse and pydev
• Stronger debugger and
IDE
– Still free, but requires
more work at install
time,
Wingware IDE
• Stronger debugger and
IDE
– Commercial release
Q&A
Thank You !
ADN Sparks
Autodesk