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Pure-Python implementation of the "ast" module

Project description

This is a pure-Python implementation of “ast” module as described in CPython documentation. It is written for the Pycopy project and is a part of its standard library, pycopy-lib.

The main component is a Python parser Implementation-wise, it’s laid out as a package, with following submodules:

  • ast.types, with AST node types auto-generated from CPython’s ASDL description.
  • ast.parser, implementing hand-written parser for Python 3.5, utilizing recursive descent to parse statements, and Pratt operator precedence parser to parse expressions.
  • ast, the main package, integrating submodules above, and exposing CPython-compatible API with corresponding additional functions and classes to process AST trees.

At the time of writing, parsers support Python 3.5 syntax with future-looking cleanups, e.g. async is treated as a keyword. Updates for the next versions of Python syntax are expected to follow.

The package has small builtin test corpus to check that the AST trees match the ones generated by CPython, and can also use entire CPython standard library as a test corpus, which it can parse similarly correctly (but with some discrepancies, e.g. this module is optimized for minimal size and doesn’t support Unicode named escape sequences (in the same way as Pycopy doesn’t support them)).

Pycopy’s ast module is written by Paul Sokolovsky and provided under the MIT license.

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