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https://github.com/python/typed_ast

Modified fork of CPython's ast module that parses `# type:` comments
https://github.com/python/typed_ast

Last synced: about 2 months ago
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Modified fork of CPython's ast module that parses `# type:` comments

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README 

        
# End of life



This project is no longer maintained.



Use the standard library `ast` module instead.

See https://github.com/python/typed_ast/issues/179.



# Typed AST



[![Build Status](https://travis-ci.org/python/typed_ast.svg?branch=master)](https://travis-ci.org/python/typed_ast)

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`typed_ast` is a Python 3 package that provides a Python 2.7 and Python 3

parser similar to the standard `ast` library.  Unlike `ast` up to Python 3.7, the parsers in

`typed_ast` include [PEP 484](https://www.python.org/dev/peps/pep-0484/) type

comments and are independent of the version of Python under which they are run.

The `typed_ast` parsers produce the standard Python AST (plus type comments),

and are both fast and correct, as they are based on the CPython 2.7 and 3.7

parsers.  `typed_ast` runs on CPython 3.6-3.10 on Linux, OS X and Windows.



**Note:** Starting with Python 3.8, we recommend to use the native `ast` parser

(see below).



## Development Philosophy



This project is a (mostly) drop-in replacement for the builtin `ast` module.  It is

intended to be bug-for-bug compatible and behave identically, except for the

presence of a few additional fields on the returned classes and a few

additional optional arguments to the `parse` call.  Therefore, `typed_ast` will

not accept any bugfixes for bugs in `ast` -- they should be fixed upstream

instead.  To avoid feature bloat, any new features for `typed_ast` should have

the potential to be broadly useful and not be built just for one niche usecase

or in a manner such that only one project can use them.



### Incompatibilities



For the purposes of *consuming* syntax trees, this should be a drop-in replacement.

It is not a drop-in replacement for users that wish to create or transform ASTs,

as a number of syntax tree classes have additional fields that must be populated

when constructing them.



Due to reliance on certain C APIs, this library does not build on and there

are [no plans to support PyPy](https://github.com/python/typed_ast/issues/111).



### Python 3.8



`typed_ast` will not be updated to support parsing Python 3.8 and

newer.  Instead, it is recommended to use the stdlib `ast` module

there, which has been augmented to support extracting type comments

and has limited support for parsing older versions of Python 3.



## Submodules

### ast3

The `ast3` parser produces the AST from a Python 3 code, up to Python 3.7. 

(For rationale and technical

details, see [here](update_process.md).)  The AST it currently produces is described in

[ast3/Parser/Python.asdl](ast3/Parser/Python.asdl).  If you wish to limit

parsing to older versions of Python 3, `ast3` can be configured to to give a

SyntaxError for new syntax features introduced beyond a given Python version.

For more information, see the module docstring in

[typed\_ast/ast3.py](typed_ast/ast3.py).



### ast27

The `ast27` parser tracks the standard Python 2.7 AST, which is expected to

never receive further updates. The AST it produces is described in

[ast27/Parser/Python.asdl](ast27/Parser/Python.asdl).  For more information,

see the module docstring in [typed\_ast/ast27.py](typed_ast/ast27.py).



### conversions

`typed_ast` also provides a `conversions` module which converts `ast27` ASTs

into `ast3` ASTs.  This functionality is somewhat experimental, however.  For

more information, see the `py2to3` docstring in

[typed\_ast/conversions](typed_ast/conversions.py).



Note: as these parsers consider type comments part of the grammar, incorrectly

placed type comments are considered syntax errors.



## Releases



To make a new `typed_ast` release, see [`release_process.md`](release_process.md).