Get information from Python module without executing it.

This is a tool and a library to work with Abstract Syntax Tree (AST) of source code in Python. It can be used to explore AST, inspect nodes and process them.

When used from command line, astdump.py can generate setup.py for your module or print its structure.

What is AST

There is a good talk What would you do with an AST? by Matthew J Desmarais with information that you will find useful.

astdump package provides dataset with generated examples of AST representation for various Python snippets. Feel free to clone repository and experiment with the code - it is safe and version controlled.

For the curious, structure of Python abstract tree is defined in

Command line usage

$ ./astdump.py 
Usage: astdump.py [options] 

AST dump tool to inspect Python source code without importing it. Can
extract values of top level vars, automatically generate setup.py and
dump structure of an Abstract Syntax Tree in readable format.

Options:
  -h, --help  show this help message and exit
  --topvars   get top level variables
  --generate  generate setup.py for a given filename

Read top level variables from Python module without importing:

$ ./astdump.py --topvars astdump.py
__author__ = 'anatoly techtonik '
__description__ = 'Extract information from Python module without importing it.'
__license__ = 'Public Domain'
__version__ = '3.0'

Automatically generate `setup.py`:

$ ./astdump.py --generate astdump.py
#!/usr/bin/env python
from distutils.core import setup

setup(
    name = 'astdump',
    version = '3.0',
    author = 'anatoly techtonik',
    author_email = 'techtonik@gmail.com',
    description = 'Extract information from Python module without importing it.',
    license = 'Public Domain',

    py_modules=['astdump'],
)

'prettyprint' AST tree:

$ ./astdump.py setup.py
Module
  ImportFrom
    alias
  Expr
    Call
      Name
        Load
      keyword
        Str
      keyword
        Str
      ...
      keyword
        Str
      keyword
        List
          Str
          Load

Library Usage

top_level_vars(filename)
Return name/value pairs for top level variables for the script specified as filename. Only string and int values are supported.

>>> import astdump
>>> astdump.top_level_vars("astdump.py")
{'__version__': '3.0', '__description__': 'Extract information from Python
module without importing it.', '__license__': 'Public Domain', '__author__
': 'anatoly techtonik '}

indented(text, printres=True)
Print indented AST for the Python code specified in text variable. The goal is to print AST as pretty as possible, so the output is likely to change. If printres is false, return string instead.

>>> import astdump
>>> astdump.indented('2+3')
Module
  Expr
    BinOp
      Num
      Add
      Num

dumpattrs(node, indent=0, oneline=False, output=sys.stdout)
Dump attributes of given node to output (sys.stdout by default). If oneline is set, format output as one line. Otherwise dump one attribute per line with the given indent.

>>> from astdump import dumpattrs as dat
>>> import ast
>>> root = ast.parse('2+3')
>>> root
<_ast.Module at 0x35f8790>
>>> dat(root)
body: [<_ast.Expr object at 0x035F8730>]
>>> dat(root.body[0])
value: <_ast.BinOp object at 0x035F8850>

Links

• pss - filetype aware grep for sources, with colors, public domain

• redhawk - AST aware grep, BSD license

• PythonJS - Python to JavaScript translator using AST, license BSD-3

• astviewer - MIT licensed ASTree viewer in Qt (PySide)

• snakefood - Python Dependency Graphs

• python-ideas -original mail about static module/package inspection that started it all
• python-static-type-checking -Group about static analysis of Python programs
• issue19557 on Python bug tracker about incomplete official AST documentation

Changes

4.3 (2016-02-14)

• fix Python 3 installation error (issue #2)

4.2 (2014-08-15)

• read __url__ for setup.py generator

4.1 (2014-08-15)

• setup.py generator tries to use module docstring for short description if __description__ is not set

4.0 (2014-06-25)

• fix setup.py generator for Python 3 (broken in 3.3)
• API changes:
  • TreeDumper() callbacks now receive stack of parent nodes instead of depth level
  • TreeDumper().level is renamed to TreeDumper().limit
  • added TreeDumper().stack list to access parent nodes
  • made TreeDumper().depth a read-only property, which returns current length of stack

3.3 (2014-03-21)

• setup.py generator is rewritten to look up missing attributes on PyPI, add classifiers and README read() for long description

3.2 (2013-11-27)

• API change:
  • dumpattrs(node) helper to print node attributes

3.1 (2013-11-20)

• fix missing dataset/ dir from source distribution

3.0 (2013-11-19)

• added dataset/ dir with snippets, output examples and update.py that regenerates them. See dataset/README.txt
• API changes:
  • added indented(text) to dump indented AST, only shows nodes for now
  • indented(text, printres=False) returns string instead of printing
  • made TreeDumper() silent by default. It just walks.
• fixed pip install, added MANIFEST.in, added trove categories, thanks to Jonathan Eunice (pull request #1)

2.0 (2013-11-10)

• API change:
  • remove --dump option, AST is dumped by default
  • add --topvars option for previous behaviour

1.2 (2013-11-10)

• fix default output for Python 2 (broken in 1.1)

1.1 (2013-09-16)

• support Python 3

1.0 (2012-03-29)

• API change:
  • get_top_vars(node) is replaced with top_level_vars(filename)

Release checklist

[ ] update version in astdump.py
[ ] run dataset/update.py for Python 2 and 3
[ ] update README.rst
[ ] python astdump.py --generate astdump.py >setup.py
[ ] check that setup.py contains unix linefeeds
[ ] setup.py sdist register upload
[ ] hg tag