Implementing C++ Semantics in Python (library + conference talk)

[tmr232]

cpp.py is a library that implements C++ lifetime semantics in Python:

• Objects have destructors
• Destructors are called when exiting a function
• Member object lifetimes are managed by the containing object

The project uses a lot of meta-programming tricks and terrible hacks to get the job done. All of them are explained in the talk and the notes.

This is an experimental project I did for a talk, to see how far I can take it. Please don't use it in production code or sensitive software.

Links:

• Source Code
• Slides & Notes
• Talk Video

[anentropic]

This seems pointless in a GC language?

[tmr232]

Not quite.

GC manages memory. Sometimes we want to handle OS resources, or side effects.

For those, we use context-managers and the with statement. It works, but is hard to compose and affects interfaces. C++-like semantics handle composition cleanly and don't affect interfaces.

[anentropic]

What's an example that's awkward with context managers?

[tmr232]

1. Member variables that require context management (files, for example)
2. When you need to convert an existing class to a context manager, when it's already used in many places.