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supported-python-syntax.md

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Supported Python syntax

Supported

PyTea’s Python parsing is dependent on the Pyright type checker. From the Python syntax, we can analyze these statements or expressions below:

  • Boolean, umber, (unformatted) String literal, Ellipsis (...), and its classes
  • Assignment, Member access, Indexing
  • Unary/Binary operation, operator overloading
  • if ...: ... elif ...: ... else: ...
  • for ... in ...: ...
  • break, continue, return, pass
  • Function/Closure definition
  • Function call
  • Variadic, keyword arguments (*args, **kwargs)
  • Class (single-inheritance)
  • __getitem__, __init__, __call__
  • global, nonlocal
  • lambda, ternary operator (... if ... else ...)
  • Tuple, List, Dictionary initialization
  • List comprehension, List/Dictionary unpacking, List slicing
  • Import local script

Unsupported

The statements below are unsupported by PyTea. These statements will be ignored or raise an error:

  • Syntax after Python 3.8 (e.g. := PEP 572)
  • Overriding augmented assignment (e.g. overriding __iadd__)
  • async, await
  • for ...: ... else: ...
  • Custom __getattr__, __setattr__, __setitem__
  • Class (multiple-inheritance)
  • Decorator, @staticmethod, @classmethod
  • Generator (yield)
  • Formatted string (e.g., f"{...}")
  • Keyword/Positional-only parameters (e.g., def f(x, /, y, *, z))
  • Set, Frozen set
  • Type annotation
  • Import 3rd-party (pip) library
  • External side-effects (File I/O, Networking, . . .)

Partially supported

The statements below can be parsed or analyzed, but we do not guarantee their analysis are correct. We will describe their behavior in PyTea.

  • while: PyTea assumes that every loop is finite. The maximum iteration counts will be bound to 300.
  • Iterator protocol (__iter__, __next__): Support of iterator protocol is still premature. Because of the finite loop assumption, an iterator instance should have constant length too. (i.e., iterator should implement __len__)
  • raise: Exception handling is not supported. If an exception is raised, the analyzer will be terminated with an error.
  • try: A except ...: ... else: ... finally: B: This will be translated to A; B
  • with A: B: This will be translated to A; B
  • assert ...: If assert condition is definitely false, PyTea will report an error without handling exception.
  • del ...: Only removing variable is supported.

For the Python builtin and 3rd-party libraries, See bin/dist/pylib directory.