Python ast (Abstract Syntax Trees): get back source string of subnode

Question

I use

>>> import ast
>>> T = ast.parse('a * (b + c)', mode='eval').body

to get an abstract syntax tree of some (mathematically looking; but this shouldn't matter) expression.

Now I want to get back the source string of some particular node. For example

>>> get_source_back(T.right)
'(b + c)'

Is there a solution for this somewhere?

(Of course I could use .walk or NodeVisitor and manually specify how to construct a string out of a node. But this does not give me the original source and I have to be careful with parentheses and so on.)

getting the source back is not a simple task, this modified version of unparse.py github.com/python/cpython/blob/master/Tools/parser/unparse.py would get the source back if using exec,pastebin.com/BUeGLdid — Padraic Cunningham
– Padraic Cunningham, Commented Aug 21, 2015 at 18:28
Possible duplicate of Given an AST, is there a working library for getting the source? — Ben Jones
– Ben Jones, Commented Jul 16, 2018 at 17:57

Patrick Maupin · Accepted Answer · 2015-08-21 19:48:16Z

2

You won't get the exact original source back. But the astor package will give you back source that will recompile identically to the original source.

Edited to add The reconstituted source provided by the version on github is substantially better than the source provided by the most recent release (e.g. fewer parentheses and better handling of docstrings). A new release is imminent, I think.

(And the unparser package mentioned in the comments pessimistically puts parentheses on everything.)

edited Aug 21, 2015 at 19:48

answered Aug 21, 2015 at 19:42

Patrick Maupin

8,1672 gold badges25 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Python ast (Abstract Syntax Trees): get back source string of subnode

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related