Question
Answer and Explanation
In the context of MyPy, the type checker for Python, disallow-untyped-defs and its counterpart allow-untyped-defs are configuration options that control how MyPy handles functions and methods without explicit type annotations.
Specifically:
1. `disallow-untyped-defs`:
- When `disallow-untyped-defs` is enabled (usually by setting it to `true` in your MyPy configuration file or through a command-line flag), MyPy will produce an error for any function or method that lacks type annotations for its parameters or return value.
- This option promotes more explicit and rigorous typing in your code, making it more maintainable, easier to understand, and less prone to type-related errors. It enforces full type coverage across your codebase for function definitions.
- For example, if you have a function like this: def add(x, y): return x + y, MyPy will report an error with disallow-untyped-defs enabled, because `x` and `y` do not have type annotations.
- To fix this, you would need to add type annotations: def add(x: int, y: int) -> int: return x + y
2. `allow-untyped-defs`:
- When `allow-untyped-defs` is enabled (typically when set to `true` or if `disallow-untyped-defs` is disabled or set to `false`), MyPy will not produce errors for function and method definitions without type annotations. This option provides more flexibility, allowing parts of your codebase to remain untyped.
- However, it's worth noting that although no errors are reported for these untyped sections, you won't benefit from MyPy's type-checking capabilities in those specific areas. This may result in latent type-related bugs.
- It is usually recommended that you disable `allow-untyped-defs` in most cases in order to take full advantage of MyPy's type checking capabilities and ensure that your codebase is type-safe and robust.
In Summary:
- The disallow-untyped-defs option enforces explicit type annotations for function parameters and return values. This is a more strict approach that can help to prevent errors and improve maintainability.
- The allow-untyped-defs option allows you to skip type annotations, which offers more flexibility but might sacrifice type safety and can make debugging harder.
- By controlling whether type annotations are required, these options give you a way to gradually adopt type checking in your projects, making the transition to statically typed Python easier.