pocketpy/docs/features/differences.md

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icon: dot title: Comparison with CPython

order: 99

cpython is the reference implementation of the Python programming language. It is written in C and is the most widely used implementation of Python.

The design goal

pkpy aims to be an alternative to lua for game scripting, not cpython for general purpose programming.

• For syntax and semantics, pkpy is designed to be as close to cpython as possible.
• For ecosystem and others, pkpy is not compatible with cpython.

pkpy supports most of the syntax and semantics of python. For performance and simplicity, some features are not implemented, or behave differently.

Unimplemented features

1. **kwargs in function definition.
2. __getattr__ and __setattr__.
3. Descriptor protocol __get__ and __set__. However, @property is implemented.
4. __slots__ in class definition.
5. import module from a directory with __init__.py.
6. One element tuple. (1,) is not supported.
7. Unpacking in list and dict literals, i.e. [1, 2, *a].
8. Access the exception object in try..except.
9. else clause in try..except.
10. Inplace methods like __iadd__ and __imul__.
11. __del__ in class definition.

Different behaviors

1. positional and keyword arguments are strictly evaluated.
2. When a generator is exhausted, StopIteration is returned instead of raised.
3. ++i and --j is an increment/decrement statement, not an expression.
4. int and float are not subclasses of bool.
5. int is not of unlimited precision. In 32 bit system, int and float is 30 bit; in 64 bit system, they are both 62 bit.
6. __ne__ is not required. Define __eq__ is enough.