7 Python 3

7.1 Introduction

Simics contains an embedded Python interpreter, and in Simics 6 this has been upgraded to Python 3.7.

In general, Python 2.7 code is not compatible with Python 3, so a porting effort is required. Python provides a tool 2to3 which converts source code from Python 2.7 syntax to Python 3 syntax. It applies textual transformations, and this can also be done selectively, to e.g. only apply transformations that maintain 2.7 compatibility.

As a start to the porting work, study official Python documentation where an overview of the new features in Python 3 is provided.

7.2 Modules with Python source files

When building a Simics module, any Python source files (listed with the PYTHON_FILES variable in the module Makefile) will be built into .pyc files for Python 3. By setting the variable PYTHON_2TO3 to 1 in the module Makefile, the .py files are first converted to Python 3 syntax by running the Python 2to3 tool, before being compiled for Python 3. When loading the module, the respective Simics version will use the corresponding .pyc files automatically.

7.3 Migration process

The migration process can be as follows:

1. Use the 2to3 tool to convert all source code to Python 3 syntax.
2. Make sure all tests work (the 2to3 tool occasionally makes mistakes).