PEPs 823 + 824 Implementation

Demo for PEPs 823 + 824

Explore the semantics of the proposals with this interactive WebAssembly demo. Write Python code in the editor, run it in your browser, or experiment in the interactive REPL.

PEP 823 - None-aware access operators

discuss.python.org thread →

📜 Read PEP 823 Specification

PEP 824 - None-coalescing operators

discuss.python.org thread →

📜 Read PEP 824 Specification

🛠️ Available Operators

▶ None-aware attribute access	`a?.b`	`_t.b if (_t := a) is not None else None`
▶ None-aware indexing	`a?[b]`	`_t[b] if (_t := a) is not None else None`
▶ None-coalescing	`a ?? b`	`_t if (_t := a) is not None else b`
▶ None-coalescing assignment	`a ??= b`	`if a is None: a = b`

Code Editor

# Example using PEP 823 None-aware operators # and PEP 824 None-coalescing operators from dataclasses import dataclass @dataclass class Data: user: User | None @dataclass class User: name: str responses = [ Data(user=User("Alex")), Data(user=None), ] for data in responses: print(f"User name: {data.user?.name ?? "unknown"}")

Terminal Output

Interactive REPL

Note: This is an experimental WebAssembly build of Python. Some features like networking, subprocesses, and threading are not available. Please report issues regarding the demo or implementation to the implementation repository .

SharedArrayBuffer, which is required for this demo, is not available in your browser environment. One common cause of this failure is loading index.html directly in your browser instead of using server.py as described in Tools/wasm/README.md .

For more details about security requirements for SharedArrayBuffer, see this MDN page.