Getting Started – Autodesk Maya Python API

Posted: October 21, 2012 in FX Pipeline, Maya

  1. Not Fully Grasping the Maya Architecture and How the Python API Leverages It
    If you don’t completely understanding the Maya architecture, command engine and the Dependency Graph, you will run into trouble as your tools get more complex. Take the time to learn these components as they are very different than any other animation product. Because of this complexity, it makes Maya more flexible and powerful than any other product. Check out the free Maya Python API webcast recording located here (www.autodesk.com/developmaya)
  1. Trying to live in a Bubble and Teach Yourself Everything
    There is no possible way to memorize or learn every single Maya API class, so don’t be shy to use the resources available. As they say “Be Resourceful” and learn from others successes, mistakes and questions. Maya has been around for over ten years, and there is lots of API information out there (www.autodesk.com/developmaya). Also, you can check out the new book “Maya Python for Games and Film: A Complete Reference for Maya Python and the Maya Python API” by Adam Mechtley and Ryan Trowbridge.

3.    The Reference Documentation is written for C++, but you are Using Python
If you do not know C++, at first glance the reference documentation will be very confusing!  But don’t worry; just put your eye blinders on to certain things when reading it. Because Python is a more simplified language than C++ (but none the less powerful), there are certain components in the documentation you can ignore. For example the class MString and MStringArray are not available in Python and instead you will work with strings as they are in native Python. Another example is that there is no MStatus class in Python and instead you will use standard Python error checking (try, except, catch). Try to think of this as having a mini translator going on in your brain, you see MStatus, so you just ignore it!

4.       The Reference Documentation is written for C++, but you are Using Python
If you do not know C++, at first glance the reference documentation will be very confusing!  But don’t worry; just put your eye blinders on to certain things when reading it. Because Python is a more simplified language than C++ (but none the less powerful), there are certain components in the documentation you can ignore. For example the class MString and MStringArray are not available in Python and instead you will work with strings as they are in native Python. Another example is that there is no MStatus class in Python and instead you will use standard Python error checking (try, except, catch). Try to think of this as having a mini translator going on in your brain, you see MStatus, so you just ignore it!

5.       Knowing when and how to Use MScriptUtil Class
Many of the API methods in Maya require that one or more of their parameters be passed as pointers or references (return values can be pointers or references as well). Because Python does not have the concept of references or pointers, you will need the utility class called MScriptUtil for working with those pointers and references in Python. MScriptUtil bridges this gap between Python and its underlying C++ API. When you see the characters * or & in the documentation for simple data types like integers and floats, think MScriptUtil!

6.  Your Python API Code is not Working, and you cannot find the Problem
When working with the Python API, like all humans, you will have errors or code you want to debug; but how the heck do you debug it? Unfortunately, there are no out-of-the-box tools in Maya, but there are some good solutions available. Cyrille Fauvel from Autodesk has integrated a Maya Python debugger into the Eclipse IDE. The details are available on Autodesk.com, at the Maya Developer Center page. Dean Edmonds also from Autodesk has integrated the PDB debugger into the Script Editor within Maya by overriding the stdin and stout functions. Also, if you Google “Python in Maya” group you will see other solutions

7.   Working with Multiple Versions of Maya Equals Multiple Versions of Python
If you are working on multiple versions of Maya, then you need to keep in mind that you will need to have multiple version of Python. Also if you are using PyQt, multiple versions of PyQt will need to be installed on your computer. As nice as it would be to use the same version of Python and PyQt for every version of Maya, it’s just not realistic as things are always improving in the Python and PyQt releases. Keep yourself educated in the Maya documentation for the versions that are used in each major release, and on which platform.

8.  Awareness of Potential Python API Performance Penalties
In certain situations when computation involves complex or many API calls, the Python API may take a performance penalty compared to the C++ API. This is because the Python API sits on top of the C++ API. This results in an extra level of conversion through C++ and as well as Python is an interpreted language which is slower by nature. For example if you are thinking of doing a Python API shader, C++ will be the better choice, but for most other tasks Python is perfect!

9.  Must use Autodesk Specific Version of Qt for Building PyQt
Building PyQt to work with Maya is a three step process. First you need to compile Qt using the Autodesk’s Modified Qt Source Code (new for 2012) that is located on the Autodesk.com site. Then you need to compile SIP (generates Python bindings for C++) against your built Qt libraries. Last, you need to compile PyQt against your built SIP libraries. Check the website for the correct versions or you could have some difficulties down the road in your tools

10. Python Plug-in Disclosure
You cannot hide your Python API code from users! If you’re a games developer looking to create Python plug-ins in-house and not worried about protecting your code, then feel free to code away. But it you want to protect, or commercialize and sell your hard work, you should consider using C++ to create your plug-ins.

11. Not Understanding the Difference between Python Script and Python API
Maya has four programming interfaces, two of which are using the Python language. It’s important to know the distinction between the terminology of Python Script and the Python API, because they each access different functionality within Maya (with very little overlap). The other two interfaces are Maya Embedded Language (MEL) and the C++ API

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