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.
Contribute
To contribute:
Fork this repository, and clone your fork.
Install the package with test dependencies (ideally in a virtualenv) with:
pip install -e '.[test]'
Run tests in your current interpreter with the command
pytest
orpython -m pytest
.Run tests across all supported interpreters with the
tox
command. You will need to have the interpreters installed separately. We recommendpyenv
for that. Usetox -p auto
to run the tests in parallel.By default certain tests which take a very long time to run are skipped, but they are run on travis CI. To run them locally, set the environment variable
ASTTOKENS_SLOW_TESTS
. For example runASTTOKENS_SLOW_TESTS=1 tox
to run the full suite of tests.