The last two technical chapters of this book introduce Python’s tools for interfacing to the outside world and discuss both its ability to be used as an embedded language tool in other systems and its interfaces for extending Python scripts with new modules and types implemented in C-compatible languages. We’ll also briefly explore other integration techniques that are less C specific, such as the Component Object Model (COM) and Jython.
Our focus in these chapters is on tight integration—where control is transferred between languages by a simple, direct, and fast in-process function call. Although it is also possible to link components of an application less directly using Inter-Process Communication (IPC) and networking tools such as sockets and pipes that we explored earlier in the book, we are interested in this part of the book in more direct and efficient techniques.
When you mix Python with components written in C (or other compiled languages) either Python or C can be “on top.” Because of that, there are two distinct integration modes and two distinct APIs:
- The extending interface
For running compiled C library code from Python programs
- The embedding interface
For running Python code from compiled C programs
Extending generally has three main roles: to optimize programs—recoding parts of a program in C is a last-resort performance boost; to leverage existing libraries—opening them up for use in Python code extends their reach; and to allow Python programs to ...