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typed-astunparse is to typed-ast as astunparse is to ast

Project Description

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

The built-in ast module can parse Python source code into AST. It can’t, however, generate source code from the AST. That’s where astunparse comes in. Using a refactored version of an obscure script found in official Python repository, it provides code generation capability for native Python AST.

The ast and astunparse modules, however, completely ignore type comments introduced in PEP 484. They treat them like all other comments, so when you parse the code using 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 where this module, typed-astunparse, comes in. It provides unparser for AST defined in typed-ast.


Python version >= 3.4.

Python libraries as specified in requirements.txt.

Tested on Linux, OS X and Windows.


For simplest installation use pip:

pip3 install typed-astunparse

You can also build your own version:

git clone
cd typed-astunparse
python3 -m unittest discover # make sure the tests pass
python3 bdist_wheel
ls -1tr dist/*.whl | tail -n 1 | xargs pip3 install


Example of roundtrip from code through AST to code:

import typed_ast.ast3
import typed_astunparse

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

for more examples see examples.ipynb notebook.

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