3. Dealing with Errors | Practical Maya Programming with Python

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Table Of Contents

Practical Maya Programming with Python

By : Galanakis

4 (12)

Practical Maya Programming with Python

4 (12)

By: Galanakis

Overview of this book

Practical Maya Programming with Python is a practical tutorial packed with plenty of examples and sample projects which guides you through building reusable, independent modules and handling unexpected errors. If you are a developer looking to build a powerful system using Python and Maya's capabilities, then this book is for you. Practical Maya Programming with Python is perfect for intermediate users with basic experience in Python and Maya who want to better their knowledge and skills.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Introspecting Maya, Python, and PyMEL

1. Introspecting Maya, Python, and PyMEL

Creating your library

Exploring Maya and PyMEL

Building the pmhelp function

Summary

2. Writing Composable Code

2. Writing Composable Code

Defining composability

Learning to use list comprehensions

Writing a skeleton converter library

Writing a character creator

Improving the performance of PyMEL

Summary

3. Dealing with Errors

3. Dealing with Errors

Understanding exceptions

Living with unhandled exceptions

Golden rules of error handling

Practical error handling in Maya

Building a high-level error handler

Installing the error handler

Improving the error handler

Summary

4. Leveraging Context Managers and Decorators in Maya

4. Leveraging Context Managers and Decorators in Maya

Inverting the subroutine

Introducing decorators

Introducing context managers

Context managers for changing scene state

Creating the denormalized_skin context manager

Creating a decorator to record metrics

Advanced decorator topics

Summary

5. Building Graphical User Interfaces for Maya

5. Building Graphical User Interfaces for Maya

Introducing Qt, PyQt, and PySide

Establishing rules for crafting a GUI

Installing PySide

Supporting PySide and PyQt

Creating the hierarchy converter GUI

Integrating the tool GUI with Maya

Working with menus

Working with Maya shelves

Summary

6. Automating Maya from the Outside

6. Automating Maya from the Outside

Controlling Maya through request-reply

Designing the automation system

Understanding the Maya startup routine

Building the request-reply automation system

Practical uses and improvements

Summary

7. Taming the Maya API

7. Taming the Maya API

Explaining types

Introducing Maya's API and architecture

Learning the Maya Python API by example

Creating a Maya Python plugin

Using PyMEL in a plugin that loads during startup

Summary

8. Unleashing the Maya API through Python

8. Unleashing the Maya API through Python

Understanding Dependency Graph plugins

Demystifying Python metaprogramming

Designing the node factory

Building the node factory

Extending the node factory

Summary

9. Becoming a Part of the Python Community

9. Becoming a Part of the Python Community

Understanding Open Source Software

Creating a site directory for third-party modules

Working with Python distributions in Maya

Contributing to the open source community

Engaging with the wider community

Summary

A. Python Best Practices

A. Python Best Practices

The args and kwargs parameters

String formatting

String concatenation

Raw strings and string literals

Path building and manipulation

Unicode strings

Using the doctest module

Adopting Test-Driven Development

Using the GitHub repository for this book

Index

Index

Practical error handling in Maya

Most of these golden rules are true in Python in general, as well as most other programming languages with exceptions. However, using Python in Maya is a different environment. There are some additional tools and constraints available. In this section, we'll go through some of the unique problems we face in Maya, and what can be done to mitigate each problem.

Dealing with expensive and mutable state

The biggest problem with error handling in Maya is that its overall design significantly constrains the choices of any system built on top of it. Consider the following script that lowercases the fileTextureName (ftn) attribute of all the file nodes in the scene:

>>> for f in pmc.ls(type='file'):
...     f.ftn.set(f.ftn.get().lower())
Traceback (most recent call last):
RuntimeError: setAttr: The attribute 'file2.fileTextureName' is locked or connected and cannot be modified.
>>> [f.ftn.get() for f in pmc.ls(type='file')]
[u'ftn0', u'FTN1', u'FTN2...

CONTINUE READING

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