User Guide

The asttokens module annotates Python abstract syntax trees (ASTs) with the positions of tokens and text in the source code that generated them.

It makes it possible for tools that work with logical AST nodes to find the particular text that resulted in those nodes, for example for automated refactoring or highlighting.

Installation

asttokens is available on PyPI: https://pypi.python.org/pypi/asttokens/:

pip install asttokens

The code is on GitHub: https://github.com/gristlabs/asttokens.

The API Reference is here: http://asttokens.readthedocs.io/en/latest/api-index.html.

Usage

ASTTokens works with both Python2 and Python3.

ASTTokens can annotate both trees built by ast, AND those built by astroid.

Here’s an example:

import asttokens, ast
source = "Robot('blue').walk(steps=10*n)"
atok = asttokens.ASTTokens(source, parse=True)

Once the tree has been marked, nodes get .first_token, .last_token attributes, and the ASTTokens object offers helpful methods:

attr_node = next(n for n in ast.walk(atok.tree) if isinstance(n, ast.Attribute))
print(atok.get_text(attr_node))
start, end = attr_node.last_token.startpos, attr_node.last_token.endpos
print(atok.text[:start] + 'RUN' + atok.text[end:])

Which produces this output:

Robot('blue').walk
Robot('blue').RUN(steps=10*n)

The ASTTokens object also offers methods to walk and search the list of tokens that make up the code (or a particular AST node), which is more useful and powerful than dealing with the text directly.

Tests

Tests are in the tests/ subdirectory. To run all tests, run:

nosetests