.. role:: bash(code) :language: bash

.. role:: python(code) :language: python

================ typed-astunparse

Unparser for Python 3 abstract syntax trees (ASTs) with type comments.

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The typed-astunparse is to typed-ast as astunparse is to ast. In short: unparsing of Python 3 abstract syntax trees (ASTs) with type comments.

.. contents:: :backlinks: none

Why this module was created

The built-in ast module can parse Python source code into AST but it can't generate source code from the AST. The astunparse module (using a refactored version of an obscure script found in official Python repository) provides code generation capability for native Python AST.

However, both ast and astunparse modules completely ignore type comments introduced in PEP 484. They treat them like all other comments, so when you parse the code using :python:compile(), your type comments will be lost. There is no place for them in the AST, so obviously they also cannot be unparsed.

The typed-ast module provides an updated AST including type comments defined in PEP 484 and a parser for Python code that contains such comments.

Unfortunately, typed-ast doesn't provide any means to go from AST back to source code with type comments. This is why module typed-astunparse (i.e. this one) was created: to provide unparser for AST defined in typed-ast.

Usage

Example of roundtrip from code through AST to code:

.. code:: python

import typed_ast.ast3
import typed_astunparse

code = 'my_string = None  # type: str'
roundtrip = typed_astunparse.unparse(typed_ast.ast3.parse(code))
print(roundtrip)

This will print:

.. code:: python

my_string = None  # type: str

for more examples see <examples.ipynb>_ notebook.

Installation

For simplest installation use :bash:pip:

.. code:: bash

pip3 install typed-astunparse

You can also build your own version:

.. code:: bash

git clone https://github.com/mbdevpl/typed-astunparse
cd typed-astunparse
pip3 install -U test_requirements.txt
python3 -m unittest  # make sure the tests pass
python3 setup.py bdist_wheel
pip3 install dist/*.whl

Requirements

Python version 3.5 or later.

Python libraries as specified in <requirements.txt>_.

Building and running tests additionally requires packages listed in <test_requirements.txt>_.

Tested on Linux, OS X and Windows.

Links

Extensions of this module

If you're extending typed-astunparse and you'd like to share why, feel free to submit a pull request <https://github.com/mbdevpl/typed-astunparse/pulls>_ introducing your project.

• horast: human-oriented ast

  Built upon both typed-ast and typed-astunparse providing parsing and unparsing of arbitrary comments in addition to type comments.

  https://pypi.org/project/horast

  https://github.com/mbdevpl/horast

Who's using this module and why

If you're using typed-astunparse in your work and you'd like to share why, feel free to submit a pull request <https://github.com/mbdevpl/typed-astunparse/pulls>_ introducing your project.

• static-typing: using typed-astunparse directly to provide AST unparsing function

  https://pypi.org/project/static-typing

  https://github.com/mbdevpl/static-typing

References

• ast:

  https://docs.python.org/3/library/ast.html

  https://greentreesnakes.readthedocs.io/

• astunparse:

  https://pypi.org/project/astunparse

  https://github.com/simonpercivall/astunparse

  https://astunparse.readthedocs.io/en/latest/

• PEP 483 - The Theory of Type Hints:

  https://www.python.org/dev/peps/pep-0483/

• PEP 484 - Type Hints:

  https://www.python.org/dev/peps/pep-0484/

• PEP 3107 - Function Annotations:

  https://www.python.org/dev/peps/pep-3107/

• PEP 526 - Syntax for Variable Annotations:

  https://www.python.org/dev/peps/pep-0526/

• typed-ast:

  https://pypi.org/project/typed-ast

  https://github.com/python/typed_ast