Pythonallow

Pythonallow is a term used in discussions of Python programming to describe a hypothetical mechanism for constraining the execution of Python code according to explicit policies. The concept centers on creating safe, auditable environments in which user-supplied or untrusted code can run without compromising host systems or sensitive data.

In a Pythonallow design, a policy defines what operations are permitted. Common elements include an allowlist of builtins and modules, a denylist for dangerous features, resource limits, and timeouts. The runtime integrates policy checks at key points such as attribute access, imports, and execution of dynamic code, with isolation from the host environment. The approach emphasizes transparency and verifiability, aiming to provide predictable safety guarantees while preserving as much language functionality as possible.

There is no official Pythonallow project in the Python ecosystem; rather, the term appears in academic papers, security discussions, and tutorials as a way to reason about sandboxing. Several experimental prototypes and restricted-interpreter environments have explored similar ideas, using techniques such as import hooks, AST rewrites, or interpreter sandboxing to enforce policies. These efforts illustrate the trade-offs between security, performance, and language flexibility in constrained execution contexts.

Use cases for a Pythonallow-like model include execution of user-submitted code in online editors, education platforms, and plugin systems where safety concerns are paramount. Limitations include the difficulty of achieving complete security in Python’s dynamic environment, potential policy evasion, performance overhead, and the need for careful maintenance as Python evolves.

See also: sandboxing, restricted Python, safe evaluation, import hooks.